System and method for electrical stimulation of the lumbar vertebral column

ABSTRACT

Disclosed methods and devices treat lower back pain from degenerated or injured intervertebral discs. Electrodes connected to a pulse generator deliver electrical impulses to nerves located within the posterior longitudinal ligament and posterior annulus fibrosus of lumbar intervertebral discs. Percutaneous and paddle leads containing the electrodes are disclosed. The percutaneous lead, designed to prevent inappropriate stimulation of the thecal sac, is inserted in the anterior epidural space using a special cannula and lead blank. Paddle leads are configured individually for implantation in each patient. The electrical stimulation may reduce back pain reversibly, with or without the simultaneous use of non-thermal irreversible electroporation. If such stimulation is unsuccessful, nerves in the ligament or annulus fibrosus may then be injured therapeutically without repositioning the lead, using impulses that result in heating, wherein a thermal insulator covers the thecal sac, thereby shielding nerves within the thecal sac from potential heat damage.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division of pending U.S. application Ser. No. 13/402,093having publication No. US 2012/0215218, which was filed 22 Feb. 2012.That application, as well as this division of that application, claimsthe benefit of provisional patent application No. 61/463,800, entitledSystem and Method for Electrical Stimulation of the Lumbar VertebralColumn, to J. D. LIPANI, with a filing date of Feb. 23, 2011, thecomplete disclosure of which is incorporated herein by reference for allpurposes.

BACKGROUND OF THE INVENTION

The field of the present invention relates to the delivery of energyimpulses to bodily tissues for therapeutic purposes, particularly theuse of implanted electrical stimulators. The disclosed methods anddevices may be used to treat discogenic lower back pain, by selectivelystimulating nerves that innervate a posterior longitudinal ligamentand/or the adjacent outer posterior annulus fibrosus of a lumbar disc.

More specifically, the present invention is directed to methods anddevices for the treatment of chronic lower back pain that may resultfrom a degenerated or injured intervertebral disc, orparaspinal-mediated low back pain.

Electrodes, along with a pulse generator that is connected to theelectrodes, are used to deliver electrical impulses to nociceptiveand/or other nerves located within the posterior longitudinal ligamentof the lumbar spine and the posterior annulus fibrosus of theintervertebral disc(s) that lies adjacent to the posterior longitudinalligament. According to the invention, the electrical stimulation in thisregion may reduce back pain in a patient reversibly, adjustably, andwith almost complete coverage of the pain-generating region, forexample, by interfering with or modulating afferent pain signals to thebrain that originate in those nerves. Alternatively, if the reversibleelectrical stimulation is unsuccessful in alleviating the back pain,electrical stimulation parameters may be selected so as to irreversiblydamage the ability of the nerves to send pain signals to the brain,using non-thermal irreversible electroporation. In a differentembodiment, the device may be used to relieve pain in the patient byirreversibly damaging nerves in the posterior longitudinal ligamentand/or posterior annulus fibrosus by joule heating and/or by dielectricheating of proteins, wherein a thermal insulator covers substantiallyall of the cauda equina or thecal sac, thereby shielding the caudaequina or thecal sac from the heat that could cause damage.

The disclosed methods involve the implantation of electricallystimulating electrodes within the anterior epidural space, adjacent tothe posterior longitudinal ligament (PLL) of the lumbar spine. Suchimplantation is disclosed in detail below, but for purposes of providingbackground information, the relevant anatomy of the spine and vertebraewill first be summarized and illustrated in FIGS. 1 to 4.

Proceeding from the neck to the tailbone, there are 7 cervical (neck)vertebrae (C1-C7), 12 thoracic vertebrae (T1-T12), and 5 lumbarvertebrae (L1-L5). This is followed by the 5 sacral and coccyx(tailbone) vertebrae, which are inserted like a wedge between the twohip bones. The present invention is concerned primarily with the lumbarvertebrae L3 to L5, although it is understood that the invention may beadapted for use in other vertebrae as well, for example, the lumbarvertebrae L1 to L3, or the sacral vertebrae.

The vertebral column comprises bony vertebral bodies that are separatedby cartilaginous intervertebral discs. A primary function of thevertebral column is to provide mechanical support for the body. Theintervertebral discs provide a cushion between the vertebral bodies,absorbing some of the axial load and also facilitating motion within thevertebral column. Each disc contains a soft gel-like center (the nucleuspulposus), which is constrained radially by an elastic outer band, theannulus fibrosus. Each vertebral body articulates with its neighboringvertebral body above and below, which allows for some degree of flexion,extension, and rotation [HUMZAH M D, Soames R W. Human intervertebraldisc: structure and function. Anat Rec 220(4, 1988):337-56].

Ligaments connect two or more bones and help stabilize joints. Thepresent invention is concerned particularly with the posteriorlongitudinal ligament (PLL), which runs axially along the interiorportion of the vertebral bodies and of the annulus fibrosus of the discsthat lie between the vertebral bodies. The PLL protects the discs andimparts stability during flexion of the body [David W. L Hukins andJudith R. Meakin. Relationship between structure and mechanical functionof the tissues of the intervertebral joint. Amer. Zool. 40(2000):42-52]. Furthermore, nerves that innervate the PLL mayparticipate in reflex loops that cause back muscles to stabilize thespine.

Thus, neural receptors in the posterior longitudinal ligament,simultaneously with the output of the receptors from other ligamentssuch as the supraspinal ligament, as well as receptors in the discs, arethought to add their neural outputs to spinal interneurons, so as toreflexly activate the multifidus and longissimus muscles of the back inorder to stabilize the spine in response to loads and movements [PANJABIMM. Clinical spinal instability and low back pain. J ElectromyogrKinesiol 13(4,2003):371-9].

The posterior longitudinal ligament may be injured (sprained, as astretch and/or tear) as the result of sudden violent contraction, suddentorsion, lifting a heavy object, or other acute mechanical events.

Because the PLL lies adjacent to the posterior annulus fibrosus of theintervertebral disc, inflammation of the disc that results fromdegeneration or herniation of the disc may secondarily contribute todysfunction of the PLL, e.g., via inflammatory mediators. The mostthoroughly investigated disease of the PLL itself is its ossification,which is more common in the cervical (70%), as compared to eitherthoracic (15%) or lumbar (15%) regions [Joji INAMASU, Bernard H. Guiotand Donald C. Sachs. Ossification of the Posterior LongitudinalLigament: An Update on Its Biology, Epidemiology, and Natural History.Neurosurgery 58(6, 2006): 1027-1039]. The PLL may also fold and compressa nerve root [BEATTY R A, Sugar O, Fox T A. Protrusion of the posteriorlongitudinal ligament simulating herniated lumbar intervertebral disc. JNeurol Neurosurg Psychiatry 31(1, 1968):61-6].

Each vertebra is composed of the above-mentioned vertebral body(anteriorly) and an arch (posteriorly). Processes protrude from eacharch and serve as points of attachment for muscles of the back. Aspinous process protrudes backwards on each arch, and transverseprocesses extend from the lateral edges of each arch. The parts of thearch between the spinous and transverse processes are known as laminae,and the parts of the arch between the transverse processes and the bodyare known as pedicles. At the point where the laminae and pedicles meet,each vertebra contains two superior articular facets and two inferiorarticular facets. The pedicle of each vertebra is notched at itssuperior and inferior edges. Together the notches from two contiguousvertebra form an opening, the intervertebral neural foramen, throughwhich spinal nerves pass.

A vertebral arch also contains an opening (the vertebral foramen) whichforms a canal through which the spinal cord passes, protecting thespinal cord and nerve roots that exit from it. Because the spinal cordstops growing in infancy while the bones of the spine continue to grow,the spinal cord in adults ends at about the level of the vertebra L1/L2.Below that vertebral level, a bundle-like structure of nerve fibers,known as the cauda equina, occupy the vertebral foramen, which emanatesfrom the terminus of the spinal cord (the conus medullaris). Thus, thelumbar vertebral foramen surrounds the spinal cord/conus medullarisabove vertebrae L1/L2 and the cauda equina nerve roots below vertebraeL1/L2. [J. D. STEWART Cauda equina disorders. Chapter 6, pp 63-74. In:Neurologic Bladder, Bowel and Sexual Dysfunction (Clare J Fowler et al,eds) Amsterdam: Elsevier Science, 2001].

The above-mentioned structures are illustrated in FIGS. 1 to 4. Featuresshown in those figures that are particularly relevant to the presentinvention include the locations of the posterior longitudinal ligament(PLL) and the annulus fibrosus of the intervertebral disc(s) that liesadjacent to the PLL. For future reference, the location of electrodes ofthe present invention, which are implanted adjacent to the PLL, is alsoshown in FIGS. 1-4 (item 6 in FIG. 1, item 6 in FIG. 2, item 6 in FIG.3, and within regions 50 and/or 51 in FIG. 4).

FIG. 1 shows the spine in a cross section perpendicular to its longaxis, cut through one of the lumbar discs. The interconnections betweenthe nerves that are shown in FIG. 1 are relevant to the mechanism bywhich the disclosed electrical stimulation of nerves innervating the PLLand annulus fibrosus may reduce back pain [EDGAR M A. The nerve supplyof the lumbar intervertebral disc. J Bone Joint Surg Br 89(9,2007):1135-9]. Structures labeled in FIG. 1 are as follows: nucleuspulposus 1; annulus fibrosus 2; anterior longitudinal ligament 3;posterior longitudinal ligament 4; thecal sac 5; electrodes of thepresent invention situated in the anterior epidural space 6; filumterminale 7; intrathecal nerve root of the cauda equina 8; ventral nerveroot 9; dorsal nerve root 10; dorsal root ganglion 11; dorsal ramus ofthe spinal nerve 12; medial branch of the dorsal ramus 13; sinuvertebralnerve (meningeal branch of the spinal nerve) 14; connecting sympatheticbranch from gray ramus to sinuvertebral nerve 15; neural radicals fromsinuvertebral nerve to disc 16; white ramus communicans 17; gray ramuscommunicans 18; sympathetic neural radicals to disc surface 19;paraspinal sympathetic ganglion 20; paraspinal sympathetic chain 21;anterior branch from sympathetic ganglion to disc surface 22; branchesfrom sympathetic ganglion to disc surface 23; and posterior epiduralspace 24. FIG. 1 is adapted from: J. Randy JINKINS. The anatomic andphysiologic basis of local, referred, and radiating lumbosacral painsyndromes related to disease of the spine. J Neuroradiol 31 (2004):163-180.

FIG. 2 shows a section of the spine viewed from the side(left-to-right). The section is angled slightly away from the midline ofthe back, so as to demonstrate many of the ligaments of the spine.Vertebral bodies are labeled T12 through S1 as shown. Structuresotherwise labeled in FIG. 2 are as follows: anterior longitudinalligament 3; posterior longitudinal ligament 4; spinal cord 26; caudaequina 27; membrane of dura mater that surrounds the spinal cord and thecauda equina (thecal sac, dural tube) containing cerebral spinal fluid5; electrodes of the present invention situated in anterior epiduralspace 6; posterior epidural space 24; anterior epidural space 25;intervertebral disc 29; ligamentum flavum 30; interspinous ligament 31;supraspinous ligament 32; sacrococcygeal ligament 33; and sacral hiatus34.

FIG. 3 shows a posterior-to-anterior view of the lumbar spine, viewedobliquely on the left side of the patient. Vertebral bodies are labeledL3 through L5 as shown. The structures that are otherwise labeled inFIG. 3 are as follows: posterior longitudinal ligament 4; electrodes ofthe present invention situated in anterior epidural space 6; membrane ofdura mater that surrounds the cauda equina (thecal sac, dural tube),containing cerebral spinal fluid 5; cauda equina nerve roots 27;intervertrbal disc 29; ligamentum flavum 30; L3 nerve root 35; L4 nerveroot 36; L5 nerve root 37; pedicle (cut) 40; lamina (cut) 41; spinousprocess 42; transverse process 43; superior articular process 44; andfacet joint 45.

The present invention electrically stimulates nerves in the PLL, theconnective tissue between the PLL and annulus fibrosus and/orperiosteum, and in the superficial layer of the dorsal aspect of theannulus fibrosus that lies under the PLL [BOGDUK N, Tynan W, Wilson A S.The nerve supply to the human lumbar intervertebral discs. J Anat 132(1,1981):39-56; EDGAR M A. The nerve supply of the lumbar intervertebraldisc. J Bone Joint Surg Br 89(9, 2007):1135-9; KOJIMA Y, Maeda T, AraiR, Shichikawa K. Nerve supply to the posterior longitudinal ligament andthe intervertebral disc of the rat vertebral column as studied byacetylcholinesterase histochemistry. I. Distribution in the lumbarregion. J Anat 169 (1990):237-46; J. H. MULLIGAN. The innervation of theligaments attached to the bodies of the vertebrae. J Anat 91(4, 1957):455-465]. FIG. 4 shows a posterior-to-anterior view of the innervationof the posterior longitudinal ligament (PLL) and of the annulus fibrosusof the intervertebral disc that lies adjacent to the PLL. In this view,many of the structures shown in FIG. 3 are removed. Structures labeledin FIG. 4 are as follows: posterior longitudinal ligament 4;intervertebral fibers of the PLL 48; vertebral (longitudinal) fibers ofthe PLL 49; sinuvertebral nerve 14; nerve root 38; pedicle (cut) 40;horizontal region that may be stimulated by the disclosed devices 50;and vertical (longitudinal) region that may be stimulated by thedisclosed devices 51.

Low back pain is extremely prevalent and is the second most commonreason for patients to seek medical attention. Pain may be elicitedduring times of overexertion that results in sprain, strain, or spasm inone or more of the muscles or ligaments in the back. If the spinebecomes overly strained or compressed, a disc may rupture or bulgeoutward. Prolonged stresses or degenerative changes facilitated byobesity, smoking, arthritis, poor posture, or unhealthy activity-relatedhabits may result in injury to the intervertebral disc, resulting inchronic discogenic-mediated low back pain [Devon I RUBIN. Epidemiologyand risk factors for spine pain. Neurol Clin 25 (2007): 353-371;MANCHIKANTI L, Singh V, Datta S, Cohen S P, Hirsch J A; American Societyof Interventional Pain Physicians. Comprehensive review of epidemiology,scope, and impact of spinal pain. Pain Physician 12(4, 2009):E35-70].

Acute back pain tends to come on suddenly, but also tends to improve ina short period of time with short-term conservative treatment, such asmedication, exercise, physical therapy or rest [ATLAS S J, Deyo R A.Evaluating and managing acute low back pain in the primary care setting.J Gen Intern Med 16(2, 2004120-31]. Chronic back pain is commonlydescribed as deep, aching, dull or burning pain in one area of the back,which may also travel down the leg(s). It tends to last a month or moreor may be a persistent unrelenting problem. Sciatica is pain that beginsin the hip and/or buttocks and travels down the back of the leg. Thereare many causes of chronic back pain, including some that are fromintra-abdominal disorders that can cause pain to be referred to theback. Other examples of causes of back pain are as follows: Aradiculopathy can be due to a pinched nerve resulting from a herniateddisc; sciatica can be due to pinched nerves in vertebrae L4-53; centralspinal stenosis is due to narrowing of the spinal canal; foraminalstenosis is due to bone spurs that protrude into the neural foramen andput pressure on a nerve root; and low back pain can also be due togradual loss of normal spinal structure associated with spondylosis,spinal osteoarthritis, and/or degenerative disc disease [MichaelDEVEREAUX. Low back pain. Med Clin N America 93 (2009):477-501; MichelleLIN. Musculoskeletal Back Pain. Chapter 51, pp 591-603. In: Rosen'sEmergency Medicine: Concepts and Clinical Practice, 7th edition (Marx JA, Hockberger R S, Walls R M, et al, eds). Philadelphia: Mosby Elsevier,2009; LAST A R, Hulbert K. Chronic low back pain: evaluation andmanagement. Am Fam Physician 79(12, 2009):1067-74; McCAMEY K, Evans P.Low back pain. Prim Care 34(1, 2007):71-82]. CHOU et al provide aflowchart to assist in the diagnosis and subsequent treatment of lowback pain [CHOU R, Qaseem A, Snow V, Casey D, Cross J T Jr, Shekelle P,Owens D K; Clinical Efficacy Assessment Subcommittee of the AmericanCollege of Physicians; American College of Physicians; American PainSociety Low Back Pain Guidelines Panel. Diagnosis and treatment of lowback pain: a joint clinical practice guideline from the American Collegeof Physicians and the American Pain Society. Ann Intern Med 147(7,2007): 478-91].

The present invention is concerned primarily with back pain that is dueto degenerative disc disease, wherein degenerative changes followingloss of hydration of the nucleus pulposus lead to circumferential orradial tears within the annulus fibrosus. Annular tears within the outerannulus stimulate the ingrowth of blood vessels and accompanyingnociceptors into the outer annulus, for example, from the overlyingposterior longitudinal ligament. Nerve endings are recruited to the areaof injury and sensitized by inflammatory cytokines and otherchemofactors. Pain transmission is then sustained by chronicinflammation and exacerbated by constant axial loading [KALLEWAARD J W,Terheggen M A, Groen G J, Sluijter M E, Derby R, Kapural L, Mekhail N,van Kleef M. (15.) Discogenic low back pain. Pain Practice 10(6,2010):560-79; Keith D. WILLIAMS and Ashley L. Park. Lower Back Pain andDisorders of Intervertebral Discs. Chapter 39, pp. 2159-2236. In:Campbell's Operative Orthopaedics, 11th edition (S. Terry Canale andJames H. Beatty, eds). Philadelphia: Mosby Elsevier, 2007; AUDETTE J F,Emenike E, Meleger A L. Neuropathic low back pain. Curr Pain HeadacheRep 9(3, 2005):168-77; HURRI H, Karppinen J. Discogenic pain. Pain112(3, 2004):225-8; FREEMONT A J, Peacock T E, Goupille P, Hoyland J A,O'Brien J, Jayson M I. Nerve ingrowth into diseased intervertebral discin chronic back pain. Lancet 350(9072, 1997):178-81].

Although the pathophysiology of degenerative disc disease isincompletely understood, it is thought that sensitization of thesenociceptors by various inflammatory repair mechanisms may lead tochronic discogenic pain [MARTIN M D, Boxell C M, Malone D G.Pathophysiology of lumbar disc degeneration: a review of the literature.Neurosurg Focus 13(2, 2002):Article 1, pp. 1-6; PENG B, Wu W, Hou S, LiP, Zhang C, Yang Y. The pathogenesis of discogenic low back pain. J BoneJoint Surg Br 87(1, 2005): 62-7; Y. AOKI, K. Takahashi, S. Ohtori & H.Moriya: Neuropathology Of Discogenic Low Back Pain: A Review. TheInternet Journal of Spine Surgery 2 (1, 2005): 1-9; WALKER M H, AndersonD G. Molecular basis of intervertebral disc degeneration. Spine J 4(6Suppl, 2004):1585-1665; BOSWELL M V, et al. Interventional techniques:evidence-based practice guidelines in the management of chronic spinalpain. Pain Physician 10(1, 2007):7-111; J. Randy JINKINS. The anatomicand physiologic basis of local, referred, and radiating lumbosacral painsyndromes related to disease of the spine. J Neuroradiol 31 (2004):163-180; SEAMAN D R, Cleveland C 3rd. Spinal pain syndromes:nociceptive, neuropathic, and psychologic mechanisms. J ManipulativePhysiol Ther 22(7, 1999):458-72; NAKAMURA S I, Takahashi K, Takahashi Y,Yamagata M, Moriya H. The afferent pathways of discogenic low-back pain.Evaluation of L2 spinal nerve infiltration. J Bone Joint Surg Br 78(4,1996):606-12; TAKEBAYASHI T, Cavanaugh J M, Kallakuri S, Chen C,Yamashita T. Sympathetic afferent units from lumbar intervertebraldiscs. J Bone Joint Surg Br 88(4, 2006):554-7].

The current standard for diagnosing discogenic pain ispressure-controlled provocative discography [TOMECEK F J, Anthony C S,Boxell C, Warren J. Discography interpretation and techniques in thelumbar spine. Neurosurg Focus 13(2, 2002):Article 13, pp 1-8; ZHANG Y G,Guo T M, Guo X, Wu S X. Clinical diagnosis for discogenic low back pain.Int J Biol Sci 5(7, 2009):647-58]. Diagnostic nerve blockade may also beused to characterize the nerve source of the low back pain [MANCHIKANTIL, Singh V, Pampati V, Damron K S, Barnhill R C, Beyer C, Cash K A.Evaluation of the relative contributions of various structures inchronic low back pain. Pain Physician 4(4, 2001)308-16].

Several therapies have been used to target the nociceptive nerve fiberswithin the affected discs in patients with discogenic back pain.Non-surgical techniques involve pain medication and physical therapywith behavioral modification [KINKADE S. Evaluation and treatment ofacute low back pain. Am Fam Physician 75(8, 2007):1181-8; Brian SWILLIAMS and Paul J. Christo. Pharmacological and interventionaltreatments for neuropathic pain. Chapter 12, pp 295-375. In: Mechanismsof Pain in Peripheral Neuropathy (M Dobretsov and J-M Zhang, eds).Trivandrum, India: Research Signpost, 2009; CHOU R, Huffman L H;American Pain Society; American College of Physicians. Nonpharmacologictherapies for acute and chronic low back pain: a review of the evidencefor an American Pain Society/American College of Physicians clinicalpractice guideline. Ann Intern Med 147(7, 2007): 492-504].

Other destructive minimally invasive and surgical techniques have beenused when conservative measures fail [BOSWELL M V, et al. Interventionaltechniques: evidence-based practice guidelines in the management ofchronic spinal pain. Pain Physician 10(1, 2007):7-111; LAVELLE W F,Lavelle E D, Smith H S. Interventional techniques for back pain. ClinGeriatr Med 24(2, 2008):345-68]. Minimally invasive techniques includeIntradiscal electrothermal therapy (IDET), which involves theapplication of heat via a needle that is inserted transcutaneously intothe disc [DERBY R, Eek B, Chen Y, O'neill C, Ryan D. IntradiscalElectrothermal Annuloplasty (IDET): A Novel Approach for TreatingChronic Discogenic Back Pain. Neuromodulation 3(2, 2000):82-8].Alternatively, radiofrequency annuloplasty is a technique used to targetthe affected area using a needle to deliver radiofrequency energy fordestructive purposes [HELM S, Hayek S M, Benyamin R M, Manchikanti L.Systematic review of the effectiveness of thermal annular procedures intreating discogenic low back pain. Pain Physician 12(1, 2009):207-32].Rather than using heat to destroy nerves in the affected area, it hasbeen proposed that they may be destroyed using ionizing radiation [U.S.Pat. No. 7,634,307, entitled Method and apparatus for treatment ofdiscogenic pain, to SWEENEY].

Surgical techniques are also used to remove a large portion of the discfollowed by a fusion procedure between the two adjoining vertebralbodies [CHOU R, Baisden J, Carragee E J, Resnick D K, Shaffer W O,Loeser J D. Surgery for low back pain: a review of the evidence for anAmerican Pain Society Clinical Practice Guideline. Spine 34(10,2009):1094-109; LAVELLE W, Carl A, Lavelle ED. Invasive and minimallyinvasive surgical techniques for back pain conditions. Med Clin North Am91(2, 2007):287-98; SCHWENDER J D, Foley K T, Holly L T, Transfeldt, EE. Minimally Invasive Posterior Surgical Approaches to the Lumbar Spine.Chapter 21, pp. 333-341 In: The Spine, Fifth Edition (Harry N.Herkowitz, Richard A. Balderston, Steven R. Garfin, Frank J. Eismont,eds). Philadelphia: Saunders/Elsevier, 2006; GRIFFITH S L, Davis R J,Hutton W C. Repair of the Anulus Fibrosus of the Lumbar Disc. Chapter 12(pp 41-48), In: Nucleus Arthroplasty Technology in Spinal Care: VolumeII-Biomechanics & Development. Davis R, Cammisa F P, Girardi F P, HuttonW C, Editors. Bloomington, Minn.: Raymedica Co, 2007].

As described in the above-cited publications, all of these techniqueshave varying degrees of success, and pain relief is generally temporary.A problem with IDET and similar minimally invasive techniques is thatdestruction of nociceptors within the posterior annulus is variable andincomplete. In addition, the offending region involving the PLL is notaddressed.

Several patents or patent applications disclose methods similar toradiofrequency annuloplasty, wherein an array of electrodes (a lead) isintroduced into the disc (but not into the epidural space adjacent tothe disc) to thermally ablate disc tissue. In U.S. Pat. No. 8,066,702,entitled Combination electrical stimulating and infusion medical deviceand method, to RITTMAN, III, et al., radiofrequency energy istransmitted to tissue surrounding the lead, thereby ablating the tissue.U.S. Pat. No. 6,772,012 and U.S. Pat. No. 7,270,659, entitled Methodsfor electrosurgical treatment of spinal tissue, to RICART et al., alsodescribe controlled heating to ablate various tissues in or around thevertebral column using a radiofrequency voltage, including possibly aposterior longitudinal ligament. A thermal ablation method that may alsobe directed to the posterior longitudinal ligament, involvingelectrosurgically coagulating nerve tissue within the posterior of theannulus fibrosus by applying heat, is disclosed in U.S. Pat. No.7,331,956, entitled Methods and apparatus for treating back pain, toHOVDA et al. Similarly, abandoned application U.S. Ser. No. 11/105,274,corresponding to publication No. US20050261754, entitled Methods andapparatus for treating back pain, to WOLOSZKO et al., describesdenervation of an intervertebral disc or a region of the posteriorlongitudinal ligament by the controlled application of heat to a targettissue. All of the methods disclosed in those patents affect theoffending region irreversibly, through the application of joule heating.In contrast, in the preferred embodiments of the present invention,electrodes are introduced to affect the offending region reversibly, notirreversibly. Alternatively, in another embodiment of the presentinvention, the offending region may be affected irreversibly, but incontrast to the above-mentioned patents, the irreversible damage is dueto electroporation, not heating. In yet another embodiment of thepresent invention, irreversible damage through heating is also possible.However, in contrast to the patents cited above, an implanted lead thatmay be initially used for reversible stimulation and non-thermalelectroporation may be used for the heating as well, withoutrepositioning, wherein the thecal sac is shielded from the heat thatcould cause damage.

Lower back pain has been treated reversibly by stimulation of the spinalcord, using electrical stimulation devices that are used generically tomodulate neuronal function [ten VAARWERK I A, Staal M J. Spinal cordstimulation in chronic pain syndromes. Spinal Cord 36(10, 1998):671-82;NORTH R B, Wetzel F T. Spinal cord stimulation for chronic pain ofspinal origin: a valuable long-term solution. Spine 27(2, 2002):2584-91;STOJANOVIC M P, Abdi S. Spinal cord stimulation. Pain Physician 5(2,2002):156-66; BAROLAT G, Sharan A. Spinal Cord Stimulation for ChronicPain Management. In Pain Management for the Neurosurgeon: Part 2,Seminars in Neurosurgery 15 (2, 2004):151-175; R. B. NORTH. Neuralinterface devices: spinal cord stimulation technology. Proceedings ofthe IEEE 96(7, 2008): 1108-1119; Allen W. BURTON, Phillip C. Phan.Spinal Cord Stimulation for Pain Management. Chapter 7, pp. 7-1 to 7-16,In: Neuroengineering (Daniel J. DiLorenzo and Joseph D. Bronzino, eds).Boca Raton: CRC Press, 2008; Steven FALOWSKI, Amanda Celii, and AshwiniSharan. Spinal cord stimulation: an update. Neurotherapeutics 5(1,2008):86-99; KUNNUMPURATH S, Srinivasagopalan R, Vadivelu N. Spinal cordstimulation: principles of past, present and future practice: a review.J Clin Monit Comput 23(5, 2009):333-9]. Other examples of electricalstimulation are deep brain stimulation for treatment of Parkinson'sdisease or other movement disorders, complex regional pain syndrome(previously referred to as reflex sympathetic dystrophy), post herpeticneuralgia and others. In addition to centrally mediated nervestimulation, peripheral nerve stimulation has also been used tosuccessfully treat neuropathic pain syndromes such as occipital,trigeminal, and post herpetic neuralgias [WHITE P F, Li S, Chiu J W.Electroanalgesia: its role in acute and chronic pain management. AnesthAnalg 92(2, 2001):505-13; STANTON-HICKS M, Salamon J. Stimulation of thecentral and peripheral nervous system for the control of pain. J ClinNeurophysiol 14(1, 1997):46-62].

Although spinal cord electrical stimulation is an established method fortreating axial lower back pain, it produces improvement in back pain inonly approximately 50% of patients [John C. OAKLEY. Spinal CordStimulation in Axial Low Back Pain: Solving the Dilemma. Pain Medicine 7(Supplement s1, 2006):558-563]. The devices used for spinal cordstimulation comprise: (1) electrodes that are implanted in the spine,and (2) a power source that delivers electrical pulses to theelectrodes. The present invention also discloses electrodes that areimplanted in the spine and a power source that powers the electricalpulses that are delivered to the electrodes.

Commercially available general-purpose electrodes and pulse generatorsthat are used for spinal cord stimulation and peripheral nervestimulation could in principle also be used to electrically stimulatethe lumbar posterior longitudinal ligament and adjoining outer posteriorannulus fibrosus of the intervertebral discs. However, as disclosedbelow, such general-purpose stimulators are not well-suited for theobjectives of the present invention. Furthermore, devices according tothe present invention are not spinal cord stimulators for treating backpain. In fact, electrodes in the present invention are placed in thecanal defined by the vertebral foramen in the lumbar region and in mostcases, below the spinal cord, where the cauda equina rather than thespinal cord occupies that opening. Heretofore, when the lumbar columnshave been stimulated with spinal cord stimulator devices, it has beenfor purposes of spasticity control or the generation of muscle activityin spinal cord injury patients, not for purposes of treating back pain[DANNER S M, Hofstoetter U S, Ladenbauer J, Rattay F, Minassian K. Canthe human lumbar posterior columns be stimulated by transcutaneousspinal cord stimulation? A modeling study. Artif Organs 35(3,2014257-62]. In order to explain differences between the presentinvention and spinal cord stimulators, the development and use of spinalcord stimulators will first be summarized.

Spinal cord electrical stimulation for the treatment of pain was firstperformed in 1967 by SHEALY and colleagues [SHEALY C N, Mortimer J T,Reswick J B. Electrical inhibition of pain by stimulation of the dorsalcolumns: preliminary clinical report. Anesth Analg 46(4, 1967):489-91].In the decade that followed, many variations in technique were tried.Electrodes were implanted at different locations relative to the spinalcord: in endodural, subdural, subarachnoid, and epidural positions. Todo so, a significant amount of spinal bone was often removed, in orderto allow placement of the electrodes (a surgical laminectomy, orcomplete removal of vertebral lamina). In other cases, a small window ofbone was drilled over the area, using less invasive techniques(laminotomy, or partial removal of vertebral lamina). Finally, minimallyinvasive techniques were developed to implant a catheter-like electrodelead percutaneously.

Rather than implanting the electrodes one-by-one, leads (also known aselectrode arrays) were developed wherein multiple electrodes weremounted on, in, or about an insulating substrate, and the lead was thenimplanted. Such leads may have the shape of a plate and are said tocontain paddle electrodes, plate electrodes, ribbon electrodes, surgicalelectrodes or laminotomy electrodes. For percutaneous implantation, theleads may also have the shape of a wire or catheter, which are said tocontain percutaneous or wire electrodes.

In almost all cases, the electrodes were implanted on the posterior sideof the spinal cord, i.e., the side most accessible from the back.However, in 1975 LARSON et al. and HOPPERSTEIN implanted electrodes onthe anterior side of the spinal column, in an attempt to improve the lowsuccess rate of spinal cord stimulation in reducing pain [Sanford J.LARSON, Anthony Sances, Joseph F. Cusick, Glenn A. Meyer, ThomasSwiontek. A comparison between anterior and posterior spinal implantsystems. Surg. Neurol. 4 (1975):180-186; Reuben HOPPENSTEIN. Electricalstimulation of the ventral and dorsal columns of the spinal cord forrelief of chronic intractable pain: preliminary report. Surg. Neurol. 4(1975):187-194]. In contrast to the present invention, though, they didnot implant the anterior electrodes within the anterior epidural space,they did not attempt to implant electrodes in the lumbar spine, and theywere not concerned with the treatment of back pain. Furthermore, theanteriorly-placed electrodes were configured to stimulate the spinalcord, which is different than the configuration that would stimulateonly nerves in the posterior longitudinal ligament and the underlyingannulus fibrosus as in the present invention.

The anterior location of the electrode in the epidural space isparticularly relevant to the present invention. The epidural space isthe space within the spinal canal lying outside the dura mater (dural orthecal sac), which contains lymphatics, spinal nerve roots, loose fattytissue, small arteries, and blood vessels. The epidural space surroundsthe dural sac and is bounded by the posterior longitudinal ligamentanteriorly, the ligamenta flava and the periosteum of the laminaeposteriorly, and the pedicles of the spinal column and theintervertebral neural foramina containing their neural elementslaterally. The space communicates freely with the paravertebral spacethrough the intervertebral neural foramina. For spinal cord stimulation,the electrodes are now invariably implanted in the posterior epiduralspace.

However, a percutaneous lead may be accidentally introduced into theanterior epidural space, which is considered to be an error, and thelead is withdrawn. Thus, FALOWSKI et al. write that “Frequently, theelectrode curves around the dural sac and ends in the ventral epiduralspace. A gentle lateral curve of the electrode shortly after its entryinto the epidural space should arouse the suspicion that it is directingventrally around the dural sac. Absolute confirmation of the ventrallocation arises from the stimulation generating violent motorcontractions or observation [by fluoroscopy] in the lateral plane whichwould readily disclose the anterior position of the electrode tip.”[Steven FALOWSKI, Amanda Celii, and Ashwini Sharan. Spinal cordstimulation: an update. Neurotherapeutics 5(1, 2008):86-99]. Thus, incontrast to the present invention, implantation of a spinal cordelectrode in the anterior epidural space is considered to be an error,and in any event, the implantation of spinal cord stimulator electrodesis not performed in the lumbar spine (e.g., L3-L5). Furthermore, in thepresent invention, the electrical stimulus is directed towards theposterior longitudinal ligament in such a way that motor contractionsare not induced by the stimulation. Applicant is unaware of thedeliberate percutaneous implantation of a spinal cord stimulator in theanterior epidural space. As disclosed herein, such deliberateimplantation in the anterior epidural space would likely involve adifferent anatomical route than the interlaminal approach that is takenfor access to the posterior epidural space. Thus, as is known from themethods for performing epidural injections, to reach the anteriorepidural space, a transforaminal anatomical approach may be taken, andfor lumbar vertebrae, a sacral route may be taken as well [Mark A.HARRAST. Epidural steroid injections for lumbar spinal stenosis. CurrRev Musculoskelet Med 1:(2008):32-38].

Spinal cord stimulation is performed for the treatment of back pain, butit involves stimulation in vertebrae other than the lumbar spine L3-L5.The vertebral location of the stimulator electrodes is selected on thebasis of the location of the patient's pain. BAROLAT et al. mapped thebody areas that may be targeted by stimulation of the spinal cord indifferent vertebrae and made the following observations concerning howbest to stimulate to treat lower back pain. “It is very difficult tostimulate the low back only, without intervening chest/abdominal wallstimulation . . . (1) the peak curve for low-back stimulation coincideswith the peak curve for the chest/abdominal wall . . . (2) thechest/abdominal wall region has a higher percentage of stimulation thanthe low back; and (3) the chest/abdominal wall area has a lowerstimulation threshold than the low back. All of these factors contributeto the challenge of being able to direct stimulation selectively to thelow back without interference from the body walls. In our experience,the best location was about T9-10, with the electrode placed strictly atthe midline.” [BAROLAT G, Massaro F, He J, Zeme S, Ketcik B. Mapping ofsensory responses to epidural stimulation of the intraspinal neuralstructures in man. J Neurosurg 78(2, 1993):233-9].

It is therefore not surprising that the effectiveness of spinal cordstimulation for lower back pain is equivocal. Most reviews of itseffectiveness have been made in connection with the treatment of FailedBack Surgery Syndrome (FBSS), which may involve pain in locations inaddition to the back (e.g., the leg). A Cochrane review of randomclinical trials for the treatment of FBSS by spinal cord stimulationconcluded that although one clinical trial does provide some limitedevidence in favor of spinal cord stimulation, the numbers are small andas a result the study fails to achieve statistical significance[MAILIS_GAGNON A, Furlan A D, Sandoval J A, Taylor R. Spinal cordstimulation for chronic pain. Cochrane Database Syst Rev. 2004;(3):CD003783, updated 2009]. Other reviews indicate that up to 40percent of such FBSS patients do not benefit substantially from spinalcord stimulation [ELDABE S, Kumar K, Buchser E, Taylor R S. An analysisof the components of pain, function, and health-related quality of lifein patients with failed back surgery syndrome treated with spinal cordstimulation or conventional medical management. Neuromodulation 13(3,2010):201-9; FREY M E, Manchikanti L, Benyamin R M, Schultz D M, Smith HS, Cohen S P. Spinal cord stimulation for patients with failed backsurgery syndrome: a systematic review. Pain Physician 12(2,2009):379-97].

Similarly, a review found that spinal cord stimulation for treatmentspecifically of discogenic pain might be useful, as evidenced by areduction in opioid usage by such patients, but the review involved onlya small number of patients [VALLEJO R, Manuel Zevallos L, Lowe J,Benyamin R. Is Spinal Cord Stimulation an Effective Treatment Option forDiscogenic Pain? Pain Pract. 2011 Jul. 29. doi:10.1111/j.1533-2500.2011.00489.x. (Epub ahead of print)]. OAKLEY reviewsthe problem of why approximately 50% of patients with lower back painare not helped by spinal cord stimulation. He suggests that advances instimulator technology may help, such as properly selecting the numberand location of stimulator electrodes, using pulse generators withindependent current control over each lead contact electrode, andoptimizing the stimulation waveform (e.g., pulse width) [John C. OAKLEY.Spinal Cord Stimulation in Axial Low Back Pain: Solving the Dilemma.Pain Medicine 7 (Supplement s1, 2006):558-563]. In regards to stimuluswaveform optimization, AL-KAISY et al. suggest that the use of highfrequency pulses may help [Adnan AL-KAISY, Iris Smet, and Jean-PierreVan Buyten. Analgesia of axial low back pain with novel spinalneuromodulation. Poster presentation #202 at the 2011 meeting of TheAmerican Academy of Pain Medicine, held in National Harbor, Md., Mar.24-27, 2011].

The above-cited literature demonstrates that the treatment of lower backpain by invasive electrical stimulation is in need of improvement. Tothat end, the present invention is motivated by the fact that theinnervation of the posterior longitudinal ligament and the underlyingannulus fibrosus may be the predominant origin of the lower back pain.Thus, KUSLICH et al. write that “ . . . we had the opportunity toperform more than 700 operations on the lumbar spine while using localanesthesia . . . . Back pain could be produced by stimulation of severallumbar tissues, but by far, the most common tissue of origin [of backpain] was the outer layer of the annulus fibrosus and posteriorlongitudinal ligament.” [KUSLICH S D, Ulstrom C L, Michael C J. Thetissue origin of low back pain and sciatica: a report of pain responseto tissue stimulation during operations on the lumbar spine using localanesthesia. Orthop Clin North Am 22(2, 1991):181-7].

To affect the innervation of the lumbar posterior longitudinal ligament,the electrodes that stimulate them need to be placed in the lumbarspine, which is not done in spinal cord stimulation for back pain. Atthat lumbar location, the cauda equina is situated posterior to theposterior longitudinal ligament. Placement of an electrode between theposterior longitudinal ligament and the cauda equina would cause thecauda equina to be stimulated, if the electrode were to stimulate in alldirections. Such stimulation of the cauda equina would be veryundesirable because it would cause leg movements resulting fromstimulation of nerve roots within the cauda equina.

In fact, there are only a few reasons for electrically stimulating thecauda equina, and they are not relevant to the treatment of discogenicback pain. Electrical stimulation of the cauda equina, through highvoltage percutaneous or transcutaneous stimulation above the lumbarvertebrae, is sometimes done in order to assess conduction in the caudaequina, which is accompanied by electromyographic activity in muscles ofa lower limb. However, this does not involve placement of an electrodein the epidural space [Maertens de NOORDHOUT A, Rothwell J C, Thompson PD, Day B L, Marsden C D. Percutaneous electrical stimulation oflumbosacral roots in man. J Neurol Neurosurg Psychiatry 51(2,1988):174-81]. Electrodes have been placed in the posterior epiduralspace in the vicinity of the conus medullaris and cauda equina, but thisis done only for purposes of mapping or monitoring, not for thetreatment of lower back pain, and not for purposes of stimulating theposterior longitudinal ligament or posterior annulus fibrosus [KOTHBAUERK F, Deletis V. Intraoperative neurophysiology of the conus medullarisand cauda equina. Childs Nerv Syst 26(2, 2010):247-53]. In anothersituation, a special electrode is used to enable restoration of at leastpartial control over lower-body functions that are directed by nervesemerging from the end of the spinal cord. The electrode is designed forintroduction into the lower end of the dura beneath the conus of thespinal cord, to float in the intrathecal space that is loosely occupiedby the sacral roots and other nerves of the cauda equina. Thus, thatelectrode is not implanted in the epidural space, and it is not intendedto treat lower back pain or stimulate the posterior longitudinalligament or posterior annulus fibrosus [U.S. Pat. No. 4,633,889,entitled Stimulation of cauda-equina spinal nerves, to TALALLA et al].

Therefore, if one wishes to electrically stimulate the lumbar posteriorlongitudinal ligament to treat back pain reversibly, but avoidstimulation of other structures adjoining the anterior epidural space,at least two problems must be addressed. One is that the electricalstimulation must be directed specifically to the posterior longitudinalligament and its underlying structures, and this involves not onlydesigning an asymmetric structure for the lead, but also the design ofdirectionality of its insertion into the patient. A second problem isthat electrodes, particularly percutaneous electrodes (wire, orcatheter-like electrodes) have a tendency to migrate or rotate, suchthat even if the electrode were initially directed to stimulate theposterior longitudinal ligament, it may eventually rotate or migrate,thereby accidentally stimulating other tissues. The present invention isdesigned to address both of these problems. It also addresses theproblem of selectively ablating the nerves if the reversible stimulationdoes not work.

These problems are not addressed in the patents that are related to thepresent invention. In U.S. Pat. No. 7,069,083, U.S. Pat. No. 7,831,306,and U.S. Pat. No. 8,086,317, all entitled System and method forelectrical stimulation of the intervertebral disc, to FINCH et al., apercutaneous (wire, or catheter) lead is placed in a disc or justoutside the outer confines of the disc, circumferentially along theentire perimeter of the annulus of the disc. The lead is not placed inthe anterior epidural space, there is no suggestion of stimulating theposterior longitudinal ligament, the electrodes do not stimulate in aparticular direction, and there is no suggestion of how rotationalmigration of its cylindrical lead might be retarded. In U.S. Pat. No.7,945,331, entitled Combination electrical stimulating and infusionmedical device and method, to VILIMS, it is suggested incidentally thathis disclosed percutaneous (wire, or catheter) lead “is well suited fortreatment of other areas along the spine to include the ventral canalalong the posterior longitudinal ligament, ventral dura, and theposterior aspect of the disc.” However, there is no suggestion as to howthe lead would be inserted or used in those locations. In one embodimentof that invention, “the electrodes are not formed circumferentiallyaround the distal portion, but are formed more linearly along one sideof the stimulation lead.” However, that patent does not suggest how suchan electrode would be inserted to selectively stimulate any particulartissue, and it does not suggest how subsequent rotational migration ofits cylindrical lead could be retarded. Furthermore, that patent isconcerned with managing sacroiliac joint pain in a sacrum of a patient,not discogenic lumbar pain. None of the above-cited patents disclosedevices that would almost completely cover a pain-generating region,such as the entire innervation of an offending lumbar posteriorlongitudinal ligament and adjacent posterior annulus fibrosus of theintervertebral disc(s).

In view of the foregoing, there is a need for a lumbar vertebral columnelectrical stimulator lead that is adapted for directional insertioninto the anterior epidural space adjacent to the posterior longitudinalligament; that will provide adjustable and reversible non-destructivemodulation of nerves in the posterior longitudinal ligament andunderlying annulus fibrosus to effectively reduce back pain, whenconnected to a pulse generator; that will cover the pain-generatingregion; that will stimulate only the posterior longitudinal ligament andunderlying annulus fibrosus, but not nearby tissue such as the caudaequina or nerve roots; that is not susceptible to accidental rotation ormigration; and that as a last resort may be used to irreversibly damagethe offending nerves, without the use of thermal ablation thatindiscriminately damages material near the offending nerves, such ascollagen in the posterior longitudinal ligament.

SUMMARY OF THE INVENTION

The present invention is directed to methods and devices for thetreatment of chronic lower back pain that may result from a degeneratedor injured intervertebral disc.

An array of electrodes, along with a pulse generator that is connectedto the electrodes, are used to deliver electrical impulses tonociceptive and/or other nerves located within the posteriorlongitudinal ligament of the lumbar spine and the outer posteriorannulus fibrosus of the intervertebral disc(s) that lies adjacent to theposterior longitudinal ligament.

According to the invention, the electrical stimulation in this regionmay reduce back pain in a patient reversibly, adjustably, and withalmost complete coverage of the pain-generating region, for example, byinterfering with or modulating afferent pain signals to the brain thatoriginate in those nerves. Alternatively, if the reversible electricalstimulation is unsuccessful in alleviating the back pain, electricalstimulation parameters may be selected so as to irreversibly damage theability of the nerves to send pain signals to the brain, usingirreversible electroporation. All stimulating electrodes areunidirectional, such that the electrodes are located on one side of theinsulating material to which they are attached, e.g., a flexible, inertsilicone elastomer (such as Silastic™) or similar flexible material, toprevent electrical stimulation to the overlying thecal sac and thenerves contained therein.

Implantation of the stimulator electrodes may involve a two-stepprocess. A temporary array of electrodes (a lead) may first be implantedtranscutaneously and attached by wires to an external (nonimplanted)pulse generator. One or more of such leads are inserted for the trialunder sterile conditions under local anesthesia, with or withoutconscious sedation. The temporary leads have electrodes that aredisposed linearly along a side of the lead. The temporary leads arestraight and thin, as compared to the permanent leads that maysubsequently be implanted, in order to facilitate transcutaneousimplantation of the temporary leads. Although temporary leads may beplaced longitudinally or horizontally, horizontal placement at one ormore vertebral levels via a transforaminal approach will be most common.For implantation of the temporary leads, epidurography is used in orderto see that the cauda equina and nerve roots are safely negotiated.Whether the lead is temporary or permanent, its implantation isaccompanied by intra-operative electrophysiologic monitoring(somatosensory-evoked potential measurement, spontaneous or triggeredelectromyography, etc.) to assess the functional integrity of the caudaequina and nerve roots and to detect if that functional integrity iscompromised during insertion and/or stimulation of the lead(s).

Because of the potential danger of accidentally stimulating the thecalsac and nerves contained therein, the temporary lead is speciallydesigned to prevent accidental rotation of electrodes of the leadtowards the thecal sac. The sides of the lead preferably comprise finsthat protrude from the main body of the lead which, when inserted intothe tissue of the anterior epidural space, will prevent rotation andmigration of the leads. Furthermore, although the body of the temporarylead may be shaped in a conventional catheter-like cylindrical form, aflat shape with a rounded or curved tip is preferable in order toprevent rotation and to maintain directionality of electrodes of thelead toward the PLL. In order to implant such flat and/or finned leadsinto a suitable position, special percutaneous implantation methods anddevices are used. Intraoperative electrophysiological monitoring is alsoused to confirm that the thecal sac is not being damaged or stimulatedby a lead, either during the lead's insertion or when electrical pulsesare applied to the lead.

If stimulation of the temporary electrodes is successful in reducingback pain, a permanent array of electrodes is implanted and attached bywires to an internal (implanted) pulse generator. The permanentelectrodes are generally disposed nonlinearly across the surface of apaddle lead (plate lead or surgical lead). The direction and route ofpermanent electrode insertion may be chosen based on the implanter'spreference and the extent of the pain generating region. The objectiveis for the electrodes to cross the path of nerves identified as thestimulation target. The permanent paddle leads are specially designed tocontour the posterior vertebral column, such that the surface area ofthe contact electrodes narrows in those regions bound by two pedicles.This configuration also aids in anchoring the leads in place. Similar totemporary leads, permanent leads may be placed horizontally along thewidth of the posterior annulus of an intervertebral disc and overlyingPLL or placed longitudinally along the PLL that spans the distancebetween one or more intervertebral discs. The length and width of theelectrode paddle leads will vary to accommodate the correspondingdimensions of the pain-generating region as measured on CT or MRI inindividual patients. If the reversible electrical stimulation is notsuccessful in alleviating the pain, the lead may also be used to damagethe nerves irreversibly, wherein non-thermal electroporation producesthe damage. In a different embodiment, the device may be used to relievepain in the patient by irreversibly damaging nerves in the posteriorlongitudinal ligament and/or posterior annulus fibrosus by joule heatingand/or by dielectric heating of proteins, wherein a thermal insulatorcovers substantially all of the cauda equina or thecal sac, therebyshielding the cauda equina or thecal sac from the heat that could causedamage.

Considered as a system, the invention comprises the followingcomponents:

1) Specially designed temporary leads (percutaneous type with linearlyarranged electrodes) and permanent leads (paddle leads with generallynonlinearly arranged electrodes), with the electrodes situated in aflexible, inert silicone elastomer (such as Silastic™) or similarflexible insulating material, wherein electrical pulses are transmittedfrom the electrodes to adjacent tissue unidirectionally.2) Pulse generators designed for internal (implanted) and for externaluse that transmit electrical pulses to the electrodes via wires, and aprogrammer that controls the pulse generator. The programmer is used toadjust each electrode's electrical pulse rate, duration, amplitude andanode/cathode configuration, as well as each electrode's state ofconnection or disconnection to the pulse generator. The programmer mayprovide control signals to the pulse generator using radiofrequency orinfrared transmission, and it may also provide power to the pulsegenerator if the pulse generator is not powered by batteries.3) Specially designed surgical aides for implantation of the leads, suchas a trocar, obturator, stylet, lead blank, introducer cannula,anchoring tabs, and tools used for connecting the electrodes to thepulse generator.

However, it should be understood that application of the methods anddevices is not limited to the examples that are given. The novelsystems, devices and methods for treating conditions using the disclosedstimulation devices are more completely described in the followingdetailed description of the invention, with reference to the drawingsprovided herewith, and in claims appended hereto. Other aspects,features, advantages, etc. will become apparent to one skilled in theart when the description of the invention herein is taken in conjunctionwith the accompanying drawings.

INCORPORATION BY REFERENCE

Hereby, all issued patents, published patent applications, andnon-patent publications that are mentioned in this specification areherein incorporated by reference in their entirety for all purposes, tothe same extent as if each individual issued patent, published patentapplication, or non-patent publication were specifically andindividually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purposes of illustrating the various aspects of the invention,there are shown in the drawings forms that are presently preferred, itbeing understood, however, that the invention is not limited by or tothe precise data, methodologies, arrangements and instrumentalitiesshown, but rather only by the claims.

FIG. 1 shows the spine in a cross section perpendicular to its longaxis, cut through one of the lumbar discs.

FIG. 2 shows a cross section of the lumbar spine viewed from the side(left-to-right).

FIG. 3 shows a posterior-to-anterior view of the lumbar spine, viewedobliquely on the left side of the patient.

FIG. 4 shows a posterior-to-anterior view of the innervation of theposterior longitudinal ligament (PLL) and of the annulus fibrosus of theintervertebral disc that lies adjacent to the PLL.

FIG. 5 shows a percutaneous flat lead and a pulse generator that may beused to stimulate nerves in the posterior longitudinal ligament andunderlying annulus fibrosus, according to the present invention. In FIG.5A, the lead is shown to be a percutaneous flat lead, and in FIG. 5B, adirectional indicator is shown to point in the correct direction whenthe lead has been inserted correctly.

FIG. 6 shows methods and devices for inserting the percutaneous lead ofFIG. 5 into the anterior epidural space of a patient. Entry into thatspace for the L4-L5 disc is shown in FIGS. 6A and 6B, in a side view andin a posterior view, respectively.

FIG. 7 shows exemplary paddle leads that may be used to stimulate nervesin the posterior longitudinal ligament and underlying annulus fibrosus,according to the present invention. The lead shown in FIG. 7A isintended to be placed horizontally within the anterior epidural space,and the lead shown in FIG. 7B is intended to be placed vertically(longitudinally) within the anterior epidural space.

FIG. 8 shows a preselected target volume to be electrically stimulatedaccording to the present invention, wherein the volume is chosen toinclude nerves of the posterior longitudinal ligament and underlyingannulus fibrosus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 5 shows an array of electrodes and a pulse generator that may beused to stimulate nerves in the posterior longitudinal ligament andunderlying annulus fibrosus, according to the present invention. Anarray of electrodes is also known as a lead. In FIG. 5A, the lead 60 isshown to be a percutaneous flat lead. The width of the lead may be, forexample, 0.5 cm. As shown, it contains eight contact electrodes 61,which are embedded in insulating material 62. For example, the contactelectrodes may be made of an alloy of platinum/iridium, and theinsulation material may be made of a flexible, inert silicone elastomer(such as Silastic™), polyurethane or silicone/polyurethane. When thelead is rotated by 90 degrees and sectioned along its axis, wires 63 areseen to connect each contact to corresponding connection points in thePulse Generator 64. The wires 63 may also be embedded in the insulatingmaterial 62. For example, the wires may be made of the conductingmaterial 35NLT-DFT-28% Ag or MP35N-DFT-28% Ag. The pulse generator 64may be powered by batteries, or it may be powered by a radio-frequencydriven passive receiver. If the pulse generator is implanted in apatient, it may be programmed through an external transmitter.

When the lead 60 is rotated by 180 degrees to show its back side, thecontact electrodes 61 are no longer visible. Instead, the locationsabove the contact electrodes (shown with dotted lines) are covered byinsulating material. Consequently, stimulation with the lead 60 occurspreferentially on one of its sides, namely, the side with exposedcontact electrodes 61.

For the invention to function properly, the exposed electrodes 61 shouldface the posterior longitudinal ligament. This is because it is intendedto stimulate nerves in the posterior longitudinal ligament andunderlying annulus fibrosus but avoid stimulating other tissue such asthe thecal sac. To assist in confirmation that the lead is orientedproperly when inserted into the patient, the lead contains one or moreradio-opaque directional indicator 65 that may be visualized usingfluoroscopy. As shown in FIG. 5B, the directional indicator 65 willpoint in the correct direction when the lead has been insertedcorrectly. The insertion of the lead may be horizontal along theintervertebral portion of the PLL 66, or it may placed vertically(longitudinally) along the vertebral portions of the PLL 67, or both. Infact, in addition to the horizontal lead at the L4/L5 disc location,another horizontal lead may be inserted at the L3/L4 disc location orother locations. The vertical lead 67 is shown in FIG. 5B to containsixteen contact electrodes, which will connect to sixteen correspondingconnection points in the pulse generator, but otherwise the longersixteen-contact lead functions like the shorter eight-contact lead.Other items labeled in FIG. 5B are intervertebral fibers of theposterior longitudinal ligament 48, vertebral fibers of the posteriorlongitudinal ligament 49, and pedicles (cut) 40.

The percutaneous lead could be cylindrical or, preferably, flat. Forpurposes of defining flatness, consider a cross section of the leadperpendicular to the long axis of the lead. If that cross section can berepresented by about four or fewer connected straight lines and at mostone curved line, then the lead is flat along the surface containing thelongest straight line. For example, the lead may be rectangular in crosssection perpendicular to its long axis, with one side of the rectanglebeing potentially much longer than its adjacent sides (as in a strap).In either case, it is preferred that the lead will have attached fins 67(which may also be called wings) that inhibit movement or rotation ofthe lead from its preferred orientation. For example, FIG. 5B shows sucha preferred lead orientation. For present purposes, a fin is defined tobe something that resembles a fin in appearance, function, or positionrelative to the main body of the electrical lead. The preferredembodiment of the lead having fins is most useful when used with methodsthat are disclosed below in connection with FIG. 6 for inserting andorienting the lead in the patient. The fins 67 are shown in FIG. 5A inthe positions that they naturally attain when they are free to move.However, it is understood that the fins 67 are also sufficientlyflexible that they may be temporarily bent, approximately flat againstthe main body of the lead, when the lead with attached fins is insertedinto the slightly larger diameter lumen of a needle, cannula, orcatheter. Fins have previously been attached to stimulator leads, butnot as in the present invention. In U.S. Pat. No. 6,654,644, entitledPacemaker electrode, to SANCHEZ-ZAMBRANO, a fin is given a serrated edgeto facilitate its removal from cardiac tissue. In U.S. Pat. No.7,894,913, entitled Systems and methods of neuromodulation stimulationfor the restoration of sexual function, to BOGGS et al, a fin comprisingnon-conductive material is shown to focus (reflect) electricalstimulation energy toward a targeted tissue region and away from anon-targeted tissue region. However, in the present invention, thefocusing of electrical stimulation is due to the arrangement ofelectrodes along one side of the lead, not to the presence of the fins.Furthermore, the fins along the side of the lead of the presentinvention could in principle be made of conducting material, forexample, material containing heavy metals that are radio-opaque, whichwould facilitate imaging of the fins with fluoroscopy. Thecharacteristics of the fins most relevant to the present invention arethat the fins should be flexible enough to be temporarily bent duringpassage through a needle or cannula, but strong enough in the unbentstate to withstand rotation when inserted into the anterior epiduralspace of the patient.

Anatomical considerations related to insertion of a percutaneous lead ofthe present invention are as follows. A venous plexus surrounded byvarious amounts of fat almost entirely fills the anterior epiduralspace. In the thoracolumbar region (T10-L2) the basivertebral veinoriginates from this venous plexus and extends into the vertebralbodies. As the size of the dural sac relative to the epidural spacedecreases at the L4-L5 level, the anterior dura falls away from theposterior longitudinal ligament, and fat fills the anterior epiduralspace. Therefore, the insertion of a lead into the midline of theanterior epidural space will likely encounter decreasing mechanicalresistance as one proceeds from L2 to L5. Consequently, if apercutaneous lead is inserted in the vertical (longitudinal) direction,the preferred direction may be from L5 to L3, as shown in FIG. 5B.Depending on the need to change the direction of the distal end of thelead during its insertion, the lead may also be inserted through aneedle or cannula having a tip that produces deflected movement of awire or some other linear element that is inserted through the needle.

Percutaneous entry into the anterior epidural space is accomplished by atransforminal route, or possibly a caudal approach via the sacral hiatusin the case of leads inserted longitudinally. Another possiblepercutaneous entry route, albeit less likely, is the posteriorlateralinterlaminal approach, especially at the level of L5 and S1 forlongitudinal lead placement. Percutaneous entry to the anterior epiduralspace is performed under fluoroscopic guidance, for example in thetransforaminal approach, wherein a needle is positioned within a safezone of the intervertebral neural foramen, most commonly within a regionjust lateral and cephalad to the margin of the inferior pedicle, dorsalto the vertebral body and caudal to the nerve root (Kambin's triangle),taking care to avoid damage to the nerve root. Endoscopic guidance mayalso be used in this and subsequent implantation steps.

The entry is shown in FIGS. 6A and 6B. Labels in those figurescorrespond to: Touhy epidural needle 70, anterior epidural space 25, L3nerve root 35, L4 nerve root 36, L5 nerve root 37, thecal sac 5, andL4-L5 left neural foramen 71. Fluoroscopic contrast agents willordinarily be injected to traverse the epidural space and outline thedorsal root ganglion, nerve root, and thecal sac, thereby making itpossible to visualize a safe insertion of the needle into the anteriorepidural space [JOHNSON B A, Schellhas K P, Pollei SR. Epidurography andtherapeutic epidural injections: technical considerations and experiencewith 5334 cases. AJNR Am J Neuroradiol 20(4, 1999):697-705]. Aposterolateral approach is an alternative to the conventionaltransforaminal approach, in cases where needle tip positioning in theanterior epidural space is difficult [I. S. LEE, S. H. Kim, J. W. Lee,S. H. Hong, J.-Y. Choi, H. S. Kang, J. W. Song, and A. K. Kwon.Comparison of the temporary diagnostic relief of transforaminal epiduralsteroid injection approaches: conventional versus posterolateraltechnique. American Journal of Neuroradiology 28 (2007): 204-208].

More specifically, a scalpel is used to make a small incision where theepidural needle will enter the skin. Under fluoroscopy, a Touhy (orsimilar) epidural needle is inserted as shown in FIG. 6. Entry into theepidural space is confirmed by the ability to blow air into it due tonegative pressure within the epidural space. Fluoroscopic contrastagents may be used at this point to assess the location of the tip ofthe needle relative to the pertinent anatomy such as the nerve root,pedicles, and edge of the thecal sac. A guide wire is then inserted intothe lumen of the needle and positioned at the border of the anteriorthecal sac and underlying PLL. The needle is then withdrawn, leaving theguide wire in place. A rigid introducer cannula is placed over the guidewire and docked on bone just lateral to the anterior edge of the thecalsac where it meets the posterior spinal column. A flexible introducercannula may also be used instead. Alternatively, an obturator may beplaced in the central opening of the introducer cannula and around theguide wire during initial advancement of the introducer cannula toprevent potential blockage of its lumen by tissues. Once the obturatoris removed, fluoroscopic contrast dye can again be used, administeredthrough the cannula, to confirm proper placement of the tip of thecannula. The shape of the cannula and the shape of its lumen is designedto accommodate the shape of the lead: round to accommodate a roundedcatheter-like lead and rectangular to accommodate a flat lead which ispreferable. The orientation of the tip or bevel of the introducercannula is known by corresponding markings on the handle of the cannula.Consequently, the orientation of the tip of the cannula and handle isknown with respect to the orientation of the lead, once the lead isdelivered through the cannula in the desired orientation (i.e., with theelectrodes directed downward towards the posterior vertebral column).Once the cannula is confirmed to be in the proper position, the lead canbe delivered through the cannula and advanced under fluoroscopy into theanterior epidural space and across the posterior vertebral column,again, making sure that the electrode contacts are directed towards thePLL and away from, or opposite, the thecal sac.

If problems arise in advancing the lead into the anterior epiduralspace, the route of the lead to its desired final position in theepidural space may be opened (tunneled). In one embodiment of theinvention, a flexible lead blank used as a trocar may be passed throughthe cannula into the anterior epidural space to create a passageway forthe placement of the lead. The lead blank is preferably made of aflexible alloy such as Type 304 stainless steel with barium sulfate tomake it radio-opaque. The tip of the lead blank is rounded like the truelead to prevent puncturing of the thecal sac during the tunnelingprocess. Once the lead blank has successfully tunneled across theposterior vertebral column in the anterior epidural space, it can beremoved and the lead can then be passed into place through theintroducer cannula as described above. An alternative method ofdelivering a temporary lead, especially one with a greater width than0.5 cm, may include the use of multiple cannulas, each with a largerlumen size than the others, introduced in succession (i.e., one over theother), until the desired lumen size will accommodate the desiredelectrode lead width. The outside and lumens of such cannulas may havecross-sectional shapes that are not circular (e.g., rectangular). Thisalternative method may or may not involve the use of a Touhy (orsimilar) epidural needle and/or guide wire.

Intra-operative electrophysiologic monitoring is performed in order toassure that the lead has not been inserted in the wrong direction and isnot defective [Thomas N. PAJEWSKI, Vincent Arlet and Lawrence H.Phillips. Current approach on spinal cord monitoring: the point of viewof the neurologist, the anesthesiologist and the spine surgeon Eur SpineJ 16(Suppl 2, 2007): 115-129; MALHOTRA, Neil R and Shaffrey, ChristopherI. Intraoperative electrophysiological monitoring in spine surgery.Spine 35(25, 2010):2167-2179]. Preliminary electrical stimulation isthen performed to test operation of the stimulator, confirming thatthere are no motor responses on the part of the patient at lowstimulation voltages. With the lead in place, the introducer cannula isthen fully removed. The lead is subsequently secured in place, e.g., byattaching to the patient's skin or possibly to an interspinous ligament.Alternatively, an anchor is used to secure the lead (e.g., U.S. Pat. No.7,899,553, entitled Lead anchor for implantable stimulation devices, toBARKER). With the lead attached to the pulse generator, the pulsegenerator is now ready to be programmed to obtain a reduction in backpain, as described below.

If a percutaneous lead like the ones shown in FIG. 5 is successful inreducing the patient's back pain after a trial period of typically oneor two weeks, replacement of that lead with one capable of simulating alarger surface area would be warranted [NORTH R B, Kidd D H, Olin J C,Sieracki J M. Spinal cord stimulation electrode design: prospective,randomized, controlled trial comparing percutaneous and laminectomyelectrodes-part I: technical outcomes. Neurosurgery 51(2, 2002):381-9].Such a larger area can be covered by electrodes mounted in a paddle lead(also known as a plate or surgical lead). Two exemplary paddle leads areshown in FIG. 7. The lead shown in FIG. 7A is intended to be placedhorizontally within the anterior epidural space, across one of thepatient's discs and across nerves within intervertebral fibers of theposterior longitudinal ligament. The lead shown in FIG. 7B is intendedto be placed vertically (longitudinally) to stimulate nerves invertebral fibers of the posterior longitudinal ligament, as well asportions of two (or more) of the patient's discs and intervertebralfibers of the PLL.

Apart from the fact that electrodes in the percutaneous lead shown inFIG. 5 are arranged linearly, which is in contrast to the electrodes inthe paddle leads shown in FIG. 7 that are disposed non-linearly acrossthe surface of the lead, the construction of the percutaneous and paddleleads are similar. In particular, all stimulating electrodes 61 of thepaddle leads are unidirectional, such that the electrode contacts arelocated on one side of the insulating substrate of the paddle 62 that ismade of a flexible, inert silicone elastomer (such as Silastic™) orsimilar material, to prevent stimulation to the overlying thecal sac andthe nerves therein. It is advantageous to use a somewhat elasticinsulating substrate, in order to accommodate changes in the geometry ofthe discs that accompany flexion and extension [PEARCY M J, Tibrewal SB. Lumbar intervertebral disc and ligament deformations measured invivo. Clin Orthop Relat Res (191, 1984):281-6].

Thus, the electrode contacts in FIG. 7A are visible in the view 95. Whenthat view is rotated by 90 degrees, as in the view labeled as 96, across section of that rotated view would reveal the electrodes 61, wires63 that connect the electrode to a pulse generator (64 in FIG. 5), andchannels 97 through which those wires run. When the view 95 is rotatedby 180 degrees to produce the view labeled as 98, the electrodes are nolonger visible. Thus, only the insulating material may be seen from thatback side (underlying electrode locations are indicated with dottedlines). The view labeled as 98 also shows how the lead is placedhorizontally across one of the patient's discs and across nerves in theintervertebral fibers of the posterior longitudinal ligament and annulusfibrosus, within the anterior epidural space. Radio-opaque directionalindicators 65 are also shown to be located within the leads, allowingthe orientation of the lead to be visualized by fluoroscopy. Suchdirectional indicators may be redundant if the arrangement of electrodesacross the lead is not symmetrical, in which case, the electrodesthemselves may also serve as directional markers.

As shown in FIG. 7B, a longitudinal (or vertical or vertebral) lead willwiden at the disc spaces to accommodate the posterior lateral margins ofthe annulus fibrosus. Such permanent paddle electrodes are speciallydesigned to contour the posterior vertebral column so that the surfacearea of the contact electrodes narrows in those regions bound by twopedicles. This anatomical consideration applies to the horizontal leadshown in FIG. 7A, as well as to the longitudinal lead shown in FIG. 7B.This configuration also aids in anchoring the leads in place. The leadshown in FIG. 7B is shown to contain 32 electrode contacts because itcovers a larger surface area than the lead shown in FIG. 7A (with 16electrode contacts). The length and width of the paddle leads will varyto accommodate the corresponding dimensions of the lumbar discs asmeasured using CT or MRI imaging. The width of the electrode paddleswill be limited to some extent by the distance between two adjacentnerve roots, as estimated from the location of pedicles 40. Thus, thepaddle electrodes shown in FIG. 7 differ from presently available spinalcord paddle leads in that the leads of the present invention should becustom fit for each patient (at least within a narrow range ofdimensions), otherwise the leads will not fit into the patient properly.The distance between two adjacent ipsilateral nerve roots shouldapproximate the ipsilateral interpedicular distance 100 (1.5-2.5 cm),which is slightly less than the contralateral interpedicular distance(2.0-3.0 cm) that varies according to the particular vertebra: 2.0-2.2cm for L3 101, 2.2-2.6 cm for L4 102, and 2.6-3.0 cm for L5 103). Thespace limitation created by the distance between two adjacent nerveroots may warrant two leads to be placed side by side in rare casesrequiring wider coverage. The longitudinal (or vertical) lead length 104will vary depending on the extent and number of discs to be included inthe stimulated area (typically 6.0 to 8.0 cm to achieve a distance thatspans from L3-L4 to L4-L5 and 8.0 to 9.0 cm if extension from L3-L4 toL5-S1 is required). For comparison, the maximum length of the horizontallead shown in FIG. 7A will be approximately the distance measured fromone side of an intervertebral disc to the other 105 (4.0-5.0 cm), and inthe perpendicular direction, the width of the horizontal lead will beapproximately the thickness or height of an intervertebral disc 106(approximately 1.0 cm).

The permanent leads contain small tabs 99 that are used to anchor thelead to bone or other relatively immobile tissue such as the annulusfibrosus, e.g., wherein sutures are passed through the tabs. Theelectrical connection going from the lead to the pulse generator can besituated at the end of the electrode paddle 108 or on the side of thepaddle 109 to accommodate the most suitable region of access forelectrode placement.

Direct access to the region via a standard laminotomy or laminectomyapproach may be used to insert the paddle lead. Thus, a small window ofbone (laminotomy) is drilled over the area using minimally invasivetechniques to allow insertion of the electrodes into the epidural space.Other times, more bone must be removed (laminectomy) to allow safe andaccurate placement of the electrodes. Such an approach may beaccomplished using a minimally invasive or open technique. Thelaminotomy may be performed, for example, by removing lamina (41 in FIG.3) of vertebrae L4 and L5, or alternatively between L5 and 51. As anexample, the initial steps of Technique 39-20 and its FIG. 39-37 inWILLIAMS and PARK describe a method for gaining access to the anteriorepidural space, into which the lead is inserted [Keith D. WILLIAMS andAshley L. Park. Lower Back Pain and Disorders of Intervertebral Discs.Chapter 39, pp. 2159-2236. In: Campbell's Operative Orthopaedics, 11thedition (S. Terry Canale and James H. Beatty, eds). Philadelphia: MosbyElsevier, 2007]. A full laminectomy involving one or more levels mayalso be required in cases in which significant central canal stenosisdoes not allow adequate space within the anterior epidural compartmentto accommodate lead placement. Once placed in the desired location, thelead is then anchored or sutured to firm and relatively immobile tissueor bone to prevent migration or displacement. Because the paddle leadhas an extensive flat surface, rotation of the lead is not an issue, andplacement of the lead with its electrodes facing the posteriorlongitudinal ligament (and its insulating back towards the thecal sac)will prevent stimulation of the thecal sac. However, if there is somenon-rotational migration of the lead, a snare method may be used toreposition the lead [MACDONALD J D, Fisher K J. Technique for steeringspinal cord stimulator electrode. Neurosurgery 69(1 Suppl Operative,2011):ons83-6]. The paddle lead may be inserted using an adaptation ofthe devices described above in connection with the temporary lead, ortools otherwise used for disc surgery may be used, adapted for operationin the anterior epidural space rather than the disc itself [U.S. Pat.No. 6,830,570, entitled Devices and techniques for a posterior lateraldisc space approach, to FREY et al]. Once the paddle lead is secured inplace, wires from the lead are attached to the pulse generator, and thepulse generator is ready to be programmed to obtain a reduction in backpain, as now described.

The stimulator leads are connected with wires to a pulse generator(implanted or external) that is similar to the ones used for spinal cordstimulation. Examples of such pulse generators are found in U.S. Pat.No. 7,979,126, entitled Orientation-independent implantable pulsegenerator, to PAYNE et al; U.S. Pat. No. 7,949,393, entitled Implantablepulse generator comprising fractional voltage converter, to VARRICHIO etal; and U.S. Pat. No. 7,930,030, entitled Implantable pulse generatorhaving current steering means, to WOODS et al. Parameters of the pulsesthat are generated by the pulse generator are selected using aprogrammer. Examples of programmers are found in U.S. Pat. No.6,622,048, entitled Implantable device programmer, to MANN et al; U.S.Pat. No. 6,249,703, entitled Handheld patient programmer for implantablehuman tissue stimulator, to STANTON et al; U.S. Pat. No. 7,359,751,entitled Clinician programmer for use with trial stimulator, to ERICKSONet al; and U.S. Pat. No. 7,738,963, entitled System and method forprogramming an implantable pulse generator, to HICKMAN et al. Power tothe pulse generator is ordinarily from a fully implantable battery, oralternatively from a radiofrequency system, wherein the power istransmitted through the skin by closely applied transmitting coils [U.S.Pat. No. 3,727,616, entitled Electronic system for the stimulation ofbiological systems, to LENZKES]. As described by LENZKES, the pulsegenerator may also be programmed via radiofrequency signaling thatcontrols the activation, intensity, distribution, and frequency ofelectrode stimulation.

The exemplary pulse generator 64 in FIG. 5A shows that each of theelectrodes of a lead may be programmed to be either disconnected orconnected to the pulse generator. If the electrode is connected, thepulse generator may in principle vary the voltage of each electrodeindependently, considering the external case of the pulse generator tobe a point of voltage reference. In principle, many types of waveformsmay be impressed by the pulse generator upon an electrode [A. R. LIBOFF.Signal shapes in electromagnetic therapies: a primer. pp. 17-37 in:Bioelectromagnetic Medicine (Paul J. Rosch and Marko S. Markov, eds.).New York: Marcel Dekker (2004)]. Unlike spinal cord stimulation, thestimulation of the present invention may be performed first withsuccessive small subsets of the electrodes of the lead (e.g., 1electrode, or 2 or 3 adjacent electrodes), in order to locate theunderlying nerves that are causing the back pain. Such a mapping willaid in the subsequent programming of the pulse generator, and it mayalso be useful for identifying where to ablate nerves in the event thatreversible stimulation is not successful. This is not to say that thecumulative pain experienced by the patient is necessarily the simplesummation of the pain emanating from individual nerves, because the painsignals from individual nerves may interact with one another to producegreater or lesser pain signals than those from nerves individually.Therefore, the stimulation of small subsets of electrodes of the leadmay be followed by simultaneous stimulation of pairs of such subsets, inorder to also map the interactions between the underlying nerves.

If the pulse generator is like the ones conventionally used for spinalcord stimulation, it will provide rectangular, biphasic, charge-balancedpulses of adjustable rate and duration to each electrode. For theconventional pulse generator, all electrode contacts connected as anodeswill have the same voltage, and all electrode contacts connected ascathodes will have the same voltage. Unipolar stimulation can be appliedonly if the case of the pulse generator is used as a distant anode.Thus, each electrode is conventionally programmed to have one of threestates: disconnected, anode, or cathode [DE VOS C C, Hilgerink M P,Buschman H P, Holsheinner J. Electrode contact configuration and energyconsumption in spinal cord stimulation. Neurosurgery 65(6 Suppl,2009):210-6]. The states V1, . . . , V8 in the pulse generator 64 inFIG. 5A represent those states.

As noted above, programming of the pulse generator may be aided bypreliminary stimulation involving successive small subsets of theelectrodes of the lead, in order to locate the underlying nerves thatare causing the back pain. More generally, for a lead containing 16 or32 electrodes, the number of possible programmed states is very large,in which case, the selection of the programmed state is preferably donewith the aid of computer simulation [HOLSHEIMER J. Computer modelling ofspinal cord stimulation and its contribution to therapeutic efficacy.Spinal Cord 36(8, 1998):531-40]. For the present invention, the modelingincorporates knowledge of the electrical properties of the disc and itssurrounding tissue [GU W Y, Justiz M A, Yao H. Electrical conductivityof lumbar annulus fibrosus: effects of porosity and fixed chargedensity. Spine 27(21, 2002):2390-5]. Pulse width is usually set tobetween 100 to 400 microseconds, but for such modeling, the pulse widthis also a variable, which affects the area of coverage [LEE D, HersheyB, Bradley K, Yearwood T. Predicted effects of pulse width programmingin spinal cord stimulation: a mathematical modeling study. Med Biol EngComput 49(7, 2011):765-74]. The result of the simulation is a set ofprogramming options, selected to preferentially stimulate nerves in apreselected target volume. This is shown in FIG. 8, where 50 is thepreselected target volume, which is chosen to include the nerves 14 thatare to be stimulated (also shown in FIG. 4). After an initial electrodeconfiguration is selected, the configuration may be reprogrammed tooptimize its effectiveness, even after the lead is implanted in thepatient [MANOLA L, Holsheinner J, Veltink P H, Bradley K, Peterson D.Theoretical investigation into longitudinal cathodal field steering inspinal cord stimulation. Neuromodulation (2, 2007):120-32].

The amplitude of the pulses is typically chosen to be between 0 and 10 Vand is set to the smallest value that significantly reduces back pain.Generally, pain relief will be experienced between 2 and 4 V, but thisdepends on the electrodes that are used. The frequency of the pulse waveis between about 0.01 and 10,000 Hz, typically between 20 and 120 Hz,and is also set to the value that most significantly reduces back pain.It is understood that “Hz” refers not only to sinusoidal cycles persecond but also to pulses per second in general.

The stimulation parameters must be adjusted empirically for eachpatient, so as to reduce the pain. Evidence for a reduction in pain maycome from the testimony of the patient, from a decrease in the need forpain medication, or from a physical examination that determines painlessranges of movement on the part of the patient. Success in reducing painmay be determined within minutes or hours after the stimulation, or itmay be gradual over the course of several days or weeks. Thus, there maybe an acute reduction in pain, followed by a reduction of pain over thecourse of days or weeks that is due to adaptation of the nervous system.In preferred embodiments of the invention, the patient is allowed toturn the stimulation on or off as the need arises, and may also adjustparameters of the stimulation to optimize the therapy. The pain might bereplaced with paresthesia that may be ignored by the patient. The reasonthat the stimulation parameters must be adjusted for each patient isrelated to the fact that the mechanisms responsible for the sensation ofpain are complex, and they may vary from patient to patient, as nowdescribed.

The afferent nerve fibers in the lumbar posterior longitudinal ligament,the dorsal aspect of the annulus fibrosus, and the connective tissuebetween the posterior longitudinal ligament and annulus fibrosus areprincipally mechanosensitive nociceptive fibers, classified into GroupIII and Group IV types, with a high mechanical threshold for activation.Most are unmyelinated, and many have free nerve endings. In somestudies, it is found that a superficial layer of the nerves isassociated with autonomic nerves, and a deeper layer may have a purelynociceptive function. Morbid mechanical stress associated with discabnormality and chemical stress induced by inflammation may sensitizeand stimulate these nociceptive fibers in ways that are not likely undernormal conditions. Such abnormal conditions may also cause growth of thenerve fibers in the direction of disc inflammation, mediated by nervegrowth factor [SEKINE M, Yamashita T, Takebayashi T, Sakamoto N, MinakiY, Ishii S. Mechanosensitive afferent units in the lumbar posteriorlongitudinal ligament. Spine 26(14, 2001): 1516-21; PENG B, Wu W, Hou S,Li P, Zhang C, Yang Y. The pathogenesis of discogenic low back pain. JBone Joint Surg Br 87(1, 2005): 62-7; COPPES M H, Marani E, Thomeer R T,Groen G J. Innervation of “painful” lumbar discs. Spine 22(20,1997):2342-9; Y. AOKI, K. Takahashi, S. Ohtori & H. Moriya:Neuropathology Of Discogenic Low Back Pain: A Review. The InternetJournal of Spine Surgery 2 (1, 2005): 1-9].

Anatomical studies show that the posterior longitudinal ligamentcontains an abundance of sympathetic nerve fibers that are also thoughtto convey pain. Posterior longitudinal ligament innervation is mostabundant compared to the posterior annulus of the disc and extendsbeyond the level of the involved disc [EDGAR MA. The nerve supply of thelumbar intervertebral disc. J Bone Joint Surg Br 89(9, 2007):1135-9;BOGDUK N, Tynan W, Wilson A S. The nerve supply to the human lumbarintervertebral discs. J Anat 132(1, 1981):39-56; von DURING M, Fricke B,Dahlmann A. Topography and distribution of nerve fibers in the posteriorlongitudinal ligament of the rat: an immunocytochemical andelectron-microscopical study. Cell Tissue Res 281(2, 1995):325-38;McCARTHY P W, Petts P, Hamilton A. RT97- and calcitonin gene-relatedpeptide-like immunoreactivity in lumbar intervertebral discs andadjacent tissue from the rat. J Anat 180 (1, 1992):15-24; AHMED M,Bjurholm A, Kreicbergs A, Schultzberg M. Neuropeptide Y, tyrosinehydroxylase and vasoactive intestinal polypeptide-immunoreactive nervefibers in the vertebral bodies, discs, dura mater, and spinal ligamentsof the rat lumbar spine. Spine 18(2, 1993):268-73; KALLAKURI S,Cavanaugh J M, Blagoev D C. An immunohistochemical study of innervationof lumbar spinal dura and longitudinal ligaments. Spine 23(4,1998):403-11; TAKEBAYASHI T, Cavanaugh J M, Kallakuri S, Chen C,Yamashita T. Sympathetic afferent units from lumbar intervertebraldiscs. J Bone Joint Surg Br 88(4, 2006):554-7; NAKAMURA S I, TakahashiK, Takahashi Y, Yamagata M, Moriya H. The afferent pathways ofdiscogenic low-back pain. Evaluation of L2 spinal nerve infiltration. JBone Joint Surg Br 78(4, 1996):606-12].

The pain signals from the posterior and posterior-lateral annulusfibrosus of the intervertebral disc, as well as the overlying posteriorlongitudinal ligament, are relayed to the brain via a complex network ofnerves. Some of these nerves are sensory branches of the sinuvertebralnerve while others are sympathetic nerves, thus creating a dual patternof innervation. Furthermore, the network of nerves spans regions aboveand below the involved disc, which likely explains the common difficultyof localizing discogenic back pain to a single vertebral level. Thecomplexity of the nerve network is such that it is difficult to identifythe circuits that are involved in the production of pain, and thosecircuits may in any event vary from individual to individual [J. RandyJINKINS. The anatomic and physiologic basis of local, referred, andradiating lumbosacral pain syndromes related to disease of the spine. JNeuroradiol 31 (2004): 163-180]. Compounding the complexity is thelikelihood that neuropeptide pools in structures such as the dorsal rootganglion may change in response to mechanical or chemical stresses[GRONBLAD M, Weinstein J N, Santavirta S. Immunohistochemicalobservations on spinal tissue innervation. A review of hypotheticalmechanisms of back pain. Acta Orthop Scand 62(6, 1991):614-22].Plasticity in the components of the central and sympathetic nervoussystem that are involved in the sensation of pain also adds to thecomplexity [KUNER R. Central mechanisms of pathological pain. Nat Med16(11, 2010):1258-66; SCHLERETH T, Birklein F. The sympathetic nervoussystem and pain. Neuromolecular Med 10(3, 2008):141-7].

Nevertheless, the above-cited references are consistent with at leastthe following mechanisms by which reversible electrical stimulation ofthe nerves in the posterior longitudinal ligament and underlying annulusfibrosus may reduce discogenic back pain. (1) The stimulation may causethe nerves in the posterior longitudinal ligament and/or posteriorannulus fibrosus to increase the mechanical force threshold above whichthe nerves generate an action potential. Thus, if there are fewernociceptive signals from these nerves, the sensation of pain maydecrease. (2) The stimulation may cause the sympathetic nerves in theposterior longitudinal ligament and/or posterior annulus fibrosus tosuppress the transmission of action potentials originating in thenociceptive nerves in the posterior longitudinal ligament and/orposterior annulus fibrosus. Under normal conditions, the sympatheticnervous system suppresses pain by this mechanism, and the electricalstimulation of the present invention may cause the sympathetic nerves tobehave normally. On the other hand, under abnormal conditions, thesympathetic nervous system enhances the transmission of actionpotentials originating in nociceptive nerves. In that case, theelectrical stimulation may cause a decreased enhancement by sympatheticnerves of the transmission of action potentials originating innociceptive nerves in the posterior longitudinal ligament and/orposterior annulus fibrosus. (3) The stimulation may cause the nerves inthe posterior longitudinal ligament and/or posterior annulus fibrosus todecrease their content of substance P and/or vasoactive-intestinalpeptide and/or calcitonin-gene-related peptide. These chemicals areassociated with inflammatory processes and pain, and their loss mayreverse the inflammatory processes and pain.

For some patients, reversible stimulation of the innervation of theposterior longitudinal ligament and underlying annulus fibrosus may beunsuccessful in significantly reducing lower back pain. For thosepatients, the stimulator lead and any implanted pulse generator may beremoved. However, before they are removed, a final attempt may be madeto reduce the back pain, this time by stimulating the nerves in anattempt to produce irreversible damage to the nerves. It is understoodthat the term “irreversible” is not synonymous with “permanent,” becauseonce the nerves are destroyed, new nerve fibers may eventually grow backinto the locations that had been occupied by the destroyed nerve fibers.Consequently, if the irreversible damage to the offending nerves issuccessful, it may be prudent to leave the stimulator in place for anextended period of time, in the event that newly ingrown nerves maythemselves eventually need to be treated or irreversibly damaged by thedevices of the invention.

As noted above in the background section, methods and devices have beenproposed for irreversibly ablating nerves in the posterior longitudinalligament, in the following patents or applications: U.S. Pat. No.6,772,012 and U.S. Pat. No. 7,270,659, entitled Methods forelectrosurgical treatment of spinal tissue, to RICART et al; U.S. Pat.No. 7,331,956, entitled Methods and apparatus for treating back pain, toHOVDA et al.; and abandoned application U.S. Ser. No. 11/105,274,corresponding to publication No. US20050261754, entitled Methods andapparatus for treating back pain, to WOLOSZKO et al. All of thosemethods are intended to affect the region of the posterior longitudinalligament (among other regions) irreversibly, through the application ofjoule heating. The heating is due to the application of radiofrequencyenergy (typically 100 kHz to 2 MHz) to the offending area after applyingan electrode there. Electrodes of the present invention could inprinciple also be used for that purpose, although it is understood thatelectrodes for thermal ablation are best designed specifically for thatpurpose [Yongmin KIM, H. Gunter Zieber, and Frank A. Yang. Uniformity ofcurrent density under stimulating electrodes. Critical Reviews inBiomedical Engineering 17(1990, 6): 585-619]. The mechanism by which thedelivered radiofrequency energy heats and ablates the tissue attemperatures generally at or above 45 C is well understood [HABASH R W,Bansal R, Krewski D, Alhafid H T. Thermal therapy, part 1: anintroduction to thermal therapy. Crit Rev Biomed Eng 34(6, 2006):459-89;DIEDERICH C J. Thermal ablation and high-temperature thermal therapy:overview of technology and clinical implementation. Int J Hyperthermia21(8, 2005): 745-53; HAVEMAN J, Van Der Zee J, Wondergem J, Hoogeveen JF, Hulshof M C. Effects of hyperthermia on the peripheral nervoussystem: a review. Int J Hyperthermia 20(4, 2004):371-91].

However, it is possible to damage tissue by electrical stimulationmechanisms other than heating, and those are the preferred mechanismsthat are used in the present invention [LEE R C, Zhang D, Hannig J.Biophysical injury mechanisms in electrical shock trauma. Annu RevBiomed Eng 2 (2000):477-509]. In particular, nonthermal irreversibleelectroporation may be used to damage tissue [DAVALOS R V, Mir I L,Rubinsky B. Tissue ablation with irreversible electroporation. AnnBiomed Eng 33(2, 2005):223-31; RUBINSKY B. Irreversible electroporationin medicine. Technol Cancer Res Treat 6(4, 2007):255-60]. Becausenonthermal irreversible electroporation permeabilizes and damages a cellmembrane without causing thermal damage, the integrity of molecules suchas collagen and elastin in the target region is generally preserved.

In electroporation, a pulse of electric field is generated between twoelectrodes (preferably first with one polarity, then with the reversepolarity). The damage to cells by electroporation is a function of theelectric field strength, the pulse duration, and the number of pulses.To damage the cells, the field should generally be greater than 680volts per cm (typically 1000 volts per cm), the pulse duration should be0.5-10 millisec (typically 1.0 millisec) separated by 10 sec to minimizethe likelihood of Joule heating. However, muscle and nerve cells mightbe damaged by electric fields as small as 60 μm, so in the presentinvention the electrical field is applied stepwise with increasing V/cmuntil the intended therapeutic effect is achieved. Damage will occurfirst to non-myelinated nerves, because the myelin of myelinated nervesprotects those nerves [DANIELS C, Rubinsky B. Electrical field andtemperature model of nonthermal irreversible electroporation inheterogeneous tissues. J Biomech Eng 131(7, 2009): 071006, pp 1-12].However, there is an abundance of non-myelenated nerves relative tomyelinated nerves in the annulus and posterior longitudinal ligament, sothe nerve damage will be significant [McCARTHY P W, Petts P, Hamilton A.RT97- and calcitonin gene-related peptide-like immunoreactivity inlumbar intervertebral discs and adjacent tissue from the rat. J Anat 180(1, 1992):15-24]. One ablative method of the present invention is toperform irreversible electroporation with relatively low electric fieldsto spare the myelinated nerve fibers, then resume reversible stimulationto neuromodulate their activities as in the preferred embodiment of thepresent invention. If the resumed reversible stimulation is notsuccessful in reducing the back pain, then irreversible electroporationcan be repeated with a higher electric field to ablate all of theoffending nerves. As with the reversible stimulation, intra-operativeelectrophysiologic monitoring is performed in order to assure that theablation does not harm the thecal sac and nerves contained therein[Thomas N. PAJEWSKI, Vincent Arlet and Lawrence H. Phillips. Currentapproach on spinal cord monitoring: the point of view of theneurologist, the anesthesiologist and the spine surgeon Eur Spine J16(Suppl 2, 2007): 115-129; MALHOTRA, Neil R and Shaffrey, ChristopherI. Intraoperative electrophysiological monitoring in spine surgery.Spine 35(25, 2010):2167-2179].

The electronics of a conventional 0 to 10V pulse generator is adapted toproduce such higher voltage electroporation pulses [Abbas POURZAKI andHossein Mirzaee. New high voltage pulse generators. Recent Patents onElectrical Engineering 2 (2009):65-76]. To irreversibly electroporate(ablate) the entire surface area covered by the lead, pulses may begenerated pairwise between many of the electrodes. An advantage oflimiting the electroporation pulses to pairs of electrodes within thelead is that it minimizes any pain that the patient may experience fromthe pulses. If two electrodes of the lead in FIG. 7A are separated by0.5 cm, then typically a 1 millisecond pulse of 500 V is applied betweenthem. The closer that the electrodes are to one another, then thesmaller the applied voltage must be in order to damage the underlyingnerve. If the parameters that are used do not reduce the pain, the pulseduration is increased, the voltage is increased (up to the limit of thepulse generator, typically 1000 V), and/or the pulsation continues every10 seconds until the pain is reduced.

If the electroporation is not successful in significantly reducing thepain, the stimulation parameters may be changed to allow joule heatingand dielectric heating of proteins to be additional mechanisms ofdamage. Thus, in the preferred embodiment of electroporation ablation,pulses are separated by at least 10 seconds to minimize the likelihoodof damage from joule heating (i.e., a stimulation frequency of less thanor equal to 0.1 Hz). This constraint may then be relaxed such thatpulses are delivered at higher frequencies, with or without simultaneousadjustment of the stimulation voltage. As the frequency is increasedgradually from 0.1 Hz to 10 kHz, joule heating will increasinglycontribute to the mechanism of ablation, provided that the amplitude'svoltage is set for a long enough time to a value greater than a voltagethat may be used for reversible stimulation. Above about 10 kHz, thedielectric heating of proteins will also contribute as a mechanism ofablation, wherein cellular proteins denature and become unable tofunction normally. This is because at those higher stimulationfrequencies, the cell membrane is no longer an effective barrier to thepassage of electrical current, and capacitive coupling of power acrosseach cell membrane permits the passage of current into the cytoplasm[LEE R C, Zhang D, Hannig J. Biophysical injury mechanisms in electricalshock trauma. Annu Rev Biomed Eng 2 (2000):477-509]. Such ablation bydielectric heating of proteins may be attempted up to the highest pulsefrequency that can be generated by the pulse generator, typically 20 kHzto 50 kHz. At such frequencies, one of the lead electrodes at a time mayserve as an active electrode, and current is collected in a much largerreturn electrode (dispersive electrode) which may comprise many of theremaining electrodes connected together electrically to the case of thepulse generator, or which may be a separate dispersive electrode if theablation is being attempted during surgery prior to removal of thepaddle lead [Yongmin KIM, H. Gunter Zieber, and Frank A. Yang.Uniformity of current density under stimulating electrodes. CriticalReviews in Biomedical Engineering 17(1990, 6): 585-619].

In order to effect a controlled thermal ablation, one or more smalltemperature sensor is mounted on the electrode side of the lead (e.g.,thermocouple, thermistor, silicon band gap temperature sensor,resistance temperature detector or other such sensor known in the art)and connected to the pulse generator, which makes a time vs. temperaturereadout available to the care-giver through the programmer. A thermaldose that is effective in ablating the nerves is applied, which is afunction of the measured temperature and duration of heating [HABASH RW, Bansal R, Krewski D, Alhafid H T. Thermal therapy, part 1: anintroduction to thermal therapy. Crit Rev Biomed Eng 34(6, 2006):459-89;DIEDERICH C J. Thermal ablation and high-temperature thermal therapy:overview of technology and clinical implementation. Int J Hyperthermia21(8, 2005): 745-53; HAVEMAN J, Van Der Zee J, Wondergem J, Hoogeveen JF, Hulshof M C. Effects of hyperthermia on the peripheral nervoussystem: a review. Int J Hyperthermia 20(4, 2004):371-91]. As with thereversible stimulation and electroporative ablation, intra-operativeelectrophysiologic monitoring is performed in order to assure that thethermal ablation does not harm the thecal sac and nerves containedtherein. A significant difference between such thermal ablation and themethods disclosed in the above-cited patents and patent applications toRICART et al, HOVDA et al, and WOLOSZKO et al. is that in the presentinvention, the insulation of the lead (62 in FIG. 7) serves not only aselectrical insulation, but also as thermal insulation, thus making itpossible to direct accumulated applied heat to the posteriorlongitudinal ligament and posterior annulus fibrosus, and yet shieldsubstantially all of the cauda equina or thecal sac from that heat. Forextra thermal protection, an extra layer of thermal insulation (e.g.,biocompatible ceramic foam) may be used to coat the side of the leadthat is placed nearest the cauda equina.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

What is claimed is:
 1. A method for relieving a discogenic lumbar backpain in a patient comprising: positioning a plurality of electrodeswithin an anterior epidural space of the patient to a position adjacentto a posterior longitudinal ligament and/or a posterior annulusfibrosus; generating one or more electrical impulses with a pulsegenerator; and transmitting the electrical impulses through saidelectrodes to a vicinity of one or more nerves in said posteriorlongitudinal ligament and/or posterior annulus fibrosus; wherein theelectrical impulses are configured to relieve the pain in the patient ina Step A followed by a Step B, wherein: Step A comprises electricalstimulation of the one or more nerves, wherein no significant heatdamage is generated in any tissue of the patient; wherein some of theone or more nerves are stimulated reversibly and/or are subjected tonon-thermal irreversible electroporation; and wherein a determination ismade that the patient finds that said stimulation without significantheat damage does not substantially relieve said pain; and Step Bcomprises irreversible electrical stimulation of the one or more nervesthat generates significant joule heating and/or dielectric heating ofproteins; wherein all nerves within a thecal sac neighboring theanterior epidural space are substantially shielded thermally from saidjoule heating and/or dielectric heating; and wherein the position of theplurality of electrodes is substantially the same during Step B as theposition of the plurality of electrodes during Step A.
 2. The method ofclaim 1 wherein the plurality of electrodes is implanted within thepatient.
 3. The method of claim 1 wherein a first electrode, selectedfrom among the plurality of electrodes, is configured to be an activeelectrode, and wherein a return or dispersive electrode is configured tocomprise one or more electrodes, selected from among the plurality ofelectrodes excluding the first electrode.
 4. The method of claim 3wherein the plurality of electrodes is disposed linearly along one sideof a shaft of electrically insulating material, and wherein any of theelectrodes selected from among the plurality of electrodes may beconfigured to be the active electrode.
 5. The method of claim 3 whereinthe plurality of electrodes is disposed non-linearly or linearly alongone side of a paddle of electrically insulating material, and whereinany of the electrodes selected from among the plurality of electrodesmay be configured to be the active electrode.
 6. The method of claim 3wherein the plurality of electrodes is stationary, and wherein differentelectrodes selected from among the plurality of electrodes aresequentially configured to be the active electrode, such that theheating occurs in parts of the posterior longitudinal ligament and/orposterior annulus fibrosus that underlie the sequentially activeelectrodes.
 7. The method of claim 1 wherein the electrical impulses aretransmitted through said electrodes substantially in one direction. 8.The method of claim 7 wherein the electrical impulses are nottransmitted substantially to a thecal sac or to a spinal nerve root. 9.The method of claim 4 wherein the shaft and the electrodes areconfigured to be positioned within the patient percutaneously.
 10. Themethod of claim 9 wherein a cannula is inserted through a neural foramenand adjacent to the anterior epidural space; and wherein the electrodesand the shaft are inserted into a lumen of said cannula.
 11. The methodof claim 9 wherein the electrically insulating material is connected toone or more fins; and wherein said fins are configured to inhibitrotation of the plurality of electrodes about a longest axis of saidelectrically insulating shaft.
 12. The method of claim 11 wherein thefins are disposed perpendicularly to a sole direction in which theelectrical impulses are transmitted.
 13. The method of claim 12, whereina lead, comprising the fins, the electrically insulating shaft, and theelectrodes disposed along one side of the shaft, is coated with athermally insulating material on a side of the lead that is opposite theelectrodes.
 14. The method of claim 1 wherein the plurality ofelectrodes is disposed along a first side of an electrically insulatingpaddle; and wherein a length, and/or a width, and/or a perimeter of saidelectrically insulating material is configured to fit within a measureddimension and/or a measured surface area of one or more lumbar discs ofthe patient, or wherein said insulating material is configured to fitwithin a measured distance between two adjacent ipsilateral nerve rootsof the patient.
 15. The method of claim 14 wherein the electricallyinsulating paddle and the plurality of electrodes are positioned to avicinity of a single intervertebral disc of the patient.
 16. The methodof claim 14 wherein the electrically insulating paddle and the pluralityof electrodes are positioned to a vicinity of two or more intervertebraldiscs of the patient and/or to a vicinity of intervening vertebralbodies of said discs.
 17. The method of claim 14 wherein a thermallyinsulating material coats a second side of the electrically insulatingpaddle, wherein the second side is opposite the first side.
 18. Themethod of claim 17 wherein the thermally insulating material comprises aceramic foam.
 19. The method of claim 1 wherein the electrical impulsescomprise rectangular pulses of adjustable rate, adjustable duration andadjustable amplitude for each electrode among the plurality ofelectrodes.
 20. The method of claim 1 wherein the electrical impulsescomprise pulses having a frequency of between about 10 kHz and 50 kHz.21. The method of claim 1 wherein the heating in a vicinity of theposterior longitudinal ligament and/or the posterior annulus fibrosus ismonitored using a temperature sensor.
 22. The method of claim 21 whereinthe temperature sensor is a thermocouple, thermistor, silicon band gaptemperature sensor, or resistance temperature detector.
 23. The methodof claim 21 wherein a duration of heating and a temperature duringheating are selected to effect a therapeutic thermal dose for thepatient.
 24. The method of claim 1 further comprising the performance ofintra-operative electrophysiological monitoring, wherein potentialdamage to nerves within the thecal sac is assessed.
 25. A device forrelieving a discogenic lumbar back pain in a patient comprising: aplurality of electrodes that is coupled to an electrical pulsegenerator; and a thermal insulator; wherein the plurality of electrodesand the thermal insulator are configured to be positioned within ananterior epidural space of the patient at a position adjacent to aposterior longitudinal ligament and/or a posterior annulus fibrosus;wherein the pulse generator is configured to transmit electricalimpulses through said electrodes; wherein the electrical impulses may beconfigured to relieve the pain in the patient through: (A) electricalstimulation of one or more nerves within the posterior longitudinalligament and/or the posterior annulus fibrosus, wherein some of the oneor more nerves are stimulated reversibly and/or are subjected tonon-thermal irreversible electroporation; and wherein no significantheat damage is generated in any tissue of the patient; and in analternate selectable configuration of the electrical impulses, through:(B) irreversible electrical stimulation of the one or more nerves thatgenerates significant joule heating and/or dielectric heating ofproteins; wherein the thermal insulator is configured to cover a thecalsac such that all nerves within said thecal sac are substantiallyshielded from said joule and/or dielectric heating; and whereinelectrical impulse configurations (A) and (B) are configured for usewhen the plurality of electrodes resides in a stationary position withinthe anterior epidural space of the patient.
 26. The device of claim 25wherein the electrodes are configured to be implanted within thepatient.
 27. The device of claim 25 wherein a first electrode selectedfrom among the plurality of electrodes may be configured to be an activeelectrode, and wherein a return or dispersive electrode may beconfigured to comprise one or more electrodes selected from among theplurality of electrodes excluding the first electrode.
 28. The device ofclaim 27 wherein the plurality of electrodes is disposed linearly alongone side of a shaft of electrically insulating material, and wherein anyof the electrodes among the plurality of electrodes may be configured tobe the active electrode.
 29. The device of claim 27 wherein theplurality of electrodes is disposed non-linearly or linearly along oneside of a paddle of electrically insulating material, and wherein any ofthe electrodes among the plurality of electrodes may be configured to bethe active electrode.
 30. The device of claim 25 wherein the electricalimpulses are configured to be transmitted through the electrodessubstantially in one direction.
 31. The device of claim 28 wherein theshaft and the electrodes are configured to be positioned within thepatient percutaneously.
 32. The device of claim 31 further comprising acannula, wherein the electrodes and the shaft are configured to beinserted into a lumen of said cannula.
 33. The device of claim 31wherein the electrically insulating shaft is connected to one or morefins; and wherein said fins are configured to inhibit rotation of theplurality of electrodes about a longest axis of said electricallyinsulating shaft when said shaft is positioned within the anteriorepidural space of the patient.
 34. The device of claim 33 wherein thefins are disposed perpendicularly to a sole direction in which theelectrical impulses are configured to be transmitted.
 35. The device ofclaim 25 wherein the plurality of electrodes is disposed nonlinearly orlinearly along a first side of an electrically insulating paddle; andwherein a length, and/or a width, and/or a perimeter of saidelectrically insulating material is configured to fit within a measureddimension and/or a measured surface area of one or more lumbar discs ofthe patient, or wherein said insulating material is configured to fitwithin a measured distance between two adjacent ipsilateral nerve rootsof the patient.
 36. The device of claim 35 wherein a thermallyinsulating material is disposed along a second side of the electricallyinsulating paddle, wherein the second side is opposite the first side.37. The device of claim 36 wherein the thermally insulating materialcomprises a ceramic foam.
 38. The device of claim 25 wherein theelectrical impulses are configured to comprise rectangular pulses ofadjustable rate, adjustable duration and adjustable amplitude for eachelectrode among the plurality of electrodes.
 39. The device of claim 25wherein the electrical impulses are configured to have a frequency ofbetween about 10 kHz and 50 kHz.
 40. The device of claim 25 furthercomprising a temperature sensor.
 41. The device of claim 40 wherein thetemperature sensor is a thermocouple, thermistor, silicon band gaptemperature sensor, or resistance temperature detector.
 42. The deviceof claim 25, and further comprising a trocar, or a guide wire, or astylet, or an introducer cannula, or an obturator, or a lead blank;wherein the trocor, or the guide wire, or the stylet, or the introducercannula, or the obturator, or the lead blank is configured for theplacement into the patient of the device of claim
 25. 43. A device forrelieving a discogenic lumbar back pain in a patient comprising: aplurality of electrodes that is coupled to an electrical pulsegenerator; and a thermal insulator; wherein the plurality of electrodesand the thermal insulator are configured to be implanted within ananterior epidural space of the patient at a fixed position adjacent to aposterior longitudinal ligament and/or a posterior annulus fibrosus;wherein the pulse generator is configured to transmit electricalimpulses through said electrodes; wherein said electrical impulses areconfigured to relieve the pain in the patient through electricalstimulation in the vicinity of one or more nerves in said posteriorlongitudinal ligament and/or said posterior annulus fibrosus; whereinsaid electrical impulses generate therapeutically significant jouleheating and/or dielectric heating of proteins; wherein a selectableelectrode among the plurality of electrodes may be configured to be anactive electrode, and wherein a return or dispersive electrode may beconfigured to comprise one or more electrodes selected from among theplurality of electrodes excluding the active electrode; and wherein thethermal insulator is configured to cover a thecal sac such that allnerves within said thecal sac are shielded to prevent an iatrogenesisthat would arise from heating of said thecal sac.